Image Sources

The Internet provides large number of potential sources when looking for a photo of a particular subject or a particular type of photograph.

Artists often need reference images when painting or drawing a specific subject.  Web designers need material for websites.  Advertisement companies need images for ads.  The reasons for needing images just go on and on.

Online sources fall into various categories.  Some websites specifically provide image for those needing them.  Other sites have images that can be freely used because the images are not protected by copyright. Those sites that fall in the first category will be referred to as Stock Image sites for the sake of convenience.

Stock Image Sites

Free Images

Some sites offer free stock images.  The reason varies, but some of these sites are run by people that simply enjoy sharing their photographs.  They don't care if someone else uses them.  Offering free photos is also a good way to generate traffic.  These sites can defray costs with advertising or even run a profit from running ads.


Wikimedia Commons
Site hosts huge amounts of material under different licensing  terms.  Some images are completely free to use, others can only be used for non-commercial purposes or require attribution when used.  Check each image thoroughly before downloading.
There is always the possibility that someone has made an error when uploading an subject they mistakenly believe is free to use, but is instead copyright protected with this site.  Pay close attention to any information related to copyright status.
Offers videos and audio files in addition to images.

PD Photo
Offers a selection of photos taken by the site owner under Creative Commons license.  (These are photos that are technically protected by copyright but the copyright owner has released for general use.  No compensation required for downloading and using them.)
Check each photo before using.  There are some that have not been released for use and are still subject to copyright restrictions.

Pixabay
Offers large selection of free photos and does not have ads.  At last check, site offered over 100,000 images. 
Site does require registration to download images without having to fill out a CAPTCHA first.
Don't ask me how they do it without charging or advertising.

Public Domain Photos
Site offers 25,000 photos free of charge at last check.  Site does have ads and accepts donations.
Site does not play well with the Opera web browser. 

Photos Public Domain
Large number of photos released for general use, free of charge.  Does have some ads and a donation button.  Offerings include textures for backgrounds in Photoshop or on websites.

Free Photos
Small collection of photo taken by website owner (and relatives), released for general use.  Does have some advertising on site and a donate option.

Public Domain Review 
Large collection of public domain resources, including images.  Images (including photographs) tend to be vintage in nature.  These images are in the public domain as a result of copyright protection expiring.   There are some more recent images that are public domain as a result of being governmental work. 
No ads, but accepts donations.  Also has links to its sources. 

My Public Domain Pictures
Images released for general use by the photographers.  Site does host ads.

These are just some of the more reliable sites that offer free images.  There are other sites that offer free images, some I encountered seemed a little questionable when it came to the information provided as to why the image was public domain or free to use.

Morguefile
A little different from the previous sites.  Images are free to use for certain purposes.   Using images in ways not specified requires permission from the photographer. 

Wikipedia has a couple of lists related to free images.  Try the Public Domain Image Resource list or the Free Image Resource list.


Fee Sites

These sites charge a fee in order to download and use an image.  The fee varies based on site and license type involved.  Why would anyone pay to use an image from one of these sites when there are images available for free?

Respectable fee based Stock Image sites have a library of images that is far more extensive than what is available at any free site.  Pixabay above offers just over 100,000 images.  Shutterstock adds more than that to its image library in a week, and currently offers over 29 million images.  (These sites share the download fee with the photographer that uploaded the image.  This gives photographers an incentive to add images to these sites that just doesn't exist with free sites.)

Fee sites also tend to have higher standards than free sites.  Most screen images before they are offered for sale.  The pricing structure varies from site to site and some sites offer inexpensive options.  Others cater to businesses that need large number of images by offering subscription services.  Users can download a certain number of images each month for a set monthly fee or download images for a low fee.  (As low as $0.20 per image, but that is on top of the subscription price.)

Many of these stock image sites do offer some free images.  These may be images rejected as being unsuitable for fee based stock images.

Shutterstock
One of the big players when it comes to stock image sites.  Currently boasts of having over 29 Million photos, vector images and stock videos in its library.  Images can either be purchased individually or buyers can purchase a subscription plan that allows downloading 25 images per day.  The subscription plan is definitely a better value for purchasers that need a large number of images on a consistent basis.

For photographers looking to become contributors, Shutterstock has a fairly stringent acceptance policy.  It can afford to be picky about contributors and images.  (The same goes for most established stock image sites.  A large library means less need for new images.)   Shutterstock is a good site to join as a contributor if you can manage it.  They get a lot of traffic and that means a greater likelihood of sales.

Dreamstime
Currently offers 18.5 Million images.  Dreamstime advertises images "as low as" $0.20.  This is for images downloaded at the lowest size offered.  This size may be enough for web graphics.  The price of images increases along with the size.  Dreamstime also offers a subscription service similar to that offered by Shutterstock.

Dreamstime offers much more information for photographers looking to contribute images that Shutterstock does. This seems to be true of the other stock image sites as well.

Deposit Photos
Roughly 14 million images "as low as" $0.15.  (Notice how the minimum price drops as the number of images offered.)  Like many other stock sites, Deposit Photos has branched out into vector images and videos.  Offers the typical per image and subscription options.

123RF
Library of over 22 million images.  Price "as low as" $0.21 per image.  Offers vector images, video and audio as well as photos.  Offers two-tiered subscription service as well as on demand pricing.  Again, the lowest price is for low resolution images.  The price increases along with resolution.

Fotolia
Advertises 24 million images.  Prices start at $0.74 per image for non-subscription plans, $0.19 for subscribers.  Also offers vector images and videos. 

Fotolia's royalty schedule is a bit more convoluted than other sites' payment schedules.  Photographers need to keep this in mind when looking to contribute to stock image sites.  Fotolia does reach a different audience than other sites, so joining makes sense for photographers even with the complex payment rules.

Bigstock Photo
Library listed as offering 15 million images.  Offers on demand and subscription options.  Prices start at $0.35 per image for subscribers and $0.99 for on demand purchases.  Again, this is for the lowest image size.  Larger images cost more.

The help center provides information for purchasers and contributors.  This includes information on commission rates for photographers.

Pond5
Pond5 is a second-tier player in the stock photo market offering roughly 8 million images in its library.  Unlike the larger stock image sites, Pond5 does not offer a subscription service.  Images are purchased individually.  (This makes sharing royalties with their contributors easier and more profitable for the photographer.)

Pond5 offers a variety of products, not just stock images.  Offerings include videos, audio clips and 3D Models.  (No top tier site offers the latter.)  Also different from the top tier sites, contributors set prices not Pond5.

Photodune
Part of a family of related websites operated by Envato.  Each sites offers a different specific type of product.  Photodune is Envato's stock photo site.  Envato offers 4 million total items spread out over its photo, audio, video and other sites.

Does not offer a subscription service for purchasers.  On demand images only. 

MostPhotos
Currently offers 5 million images.  Subscription plans are available as well as on demand sales.

For contributors, Mostphotos does not have a review process before images are offered for sale.  (They expect that purchasers will reject anything unsuitable.)  This makes uploading images easier for photographers and decreases staffing needs on part of the site.

iStockphoto
The fact that this site does not advertise the number of images in its library may say something about the site.

Joining iStockphoto as a photographer or artists really only makes sense under exclusivity arrangement.  The royalty payout drops dramatically if files are offered on another stock site.

VectorStock
Site specializes in vector images instead of photos.  Similar to photo stock site in other respects.  With pricing depending on the complexitiy of the image as well as size.


Non-Stock Sites

DeviantART
This is primarily an art/photo sharing site.  Some people have accounts set up to provide stock images.  There are also groups devoted to stock images.  (To make searching easier, start with the stock filter set.)

Some stock images have restrictions placed on how they can be utilized.  Often this is limiting to use as reference material for artwork.  Pay close attention to each artist's or group's rules when it comes to the use of images they offer as stock.


Government Sites/Science Organizations
Images produced by government or taxpayer funded organizations may fall into the public domain (Tax money means the public paid for it, they therefore own it.)  Government web sites or taxpayer funded groups can be a useful resources for public domain images.

There is no guarantee that any particular image on a Government website is public domain.  There is always the possibility that the website paid a licensing fee to the copyright owner in order to use the image on the site. 

Always double check image ownership before using one found on a Government web site or a site ran by a taxpayer funded group.

Science Image
Image site for CSIRO, an Australian science organization.  Images and videos on the site are not public domain,but have been released under a Creative Commons license.  (Read terms before using.)