Wikimedia Commons: an artist's resource

Licensing: I, the copyright holder of this work, release this work into the public domain. This applies worldwide.

When you want to use someone else's photo or photographic image in your latest creation, it's not safe to use just any old picture you find in a Google search.  This is especially true if you want to sell what you're creating.  By using any image you find, you may be treading on someone's copyright toes.

As lovely as they are, Flickr images, and images posted to other user galleries, can be just as tricky.  Most users aren't that interested in (but they will be if your work goes viral) or knowledgeable about what rights to grant, if any.  If  you've found the absolutely perfect picture to mix into your work, best to contact the user who posted it and ask permission.  Tell her/him what you're working on and how you will use the picture.  And save a copy of the email granting permission to use it.

It's much safer to use Wikimedia Commons where only free, non-commercial content is allowed.  The terms of Fair use are clearly defined and allow commercial use in derivative works; take a look at this page for detailed information: Commons:Reusing content outside Wikimedia.  

On the page cited above is the following information, which most applies to an artist's wanting to use someone else's photo for derivative work:

CC-BY

In the Creative Commons Attribution license (CC-BY), re-users are free to make derivative works and copy, distribute, display, and perform the work, even commercially.
You must attribute the work to the author(s), and when re-using the work or distributing it, you must mention the license terms or a link to them. You may choose whether to make future modified versions available under CC-BY.

• CC-BY-3.0 page on Creative Commons
• Full legal text of this license

CC-SA

In the Creative Commons ShareAlike license (CC-SA), re-users are free to make derivative works and copy, distribute, display, and perform the work, even commercially.
When re-using the work or distributing it, you must mention the license terms or a link to them. You must make your version available under CC-SA.

CC-BY-SA

In the Creative Commons Attribution-ShareAlike license (CC-BY-SA), re-users are free to make derivative works and copy, distribute, display, and perform the work, even commercially.
When re-using the work or distributing it, you must attribute the work to the author(s) and you must mention the license terms or a link to them. You must make your version available under CC-BY-SA.

There is also public domain, which one would think is open for any use.  But every country has its own rules.  Here's what Wikimedia says about public domain:

Content marked as public domain (or local equivalent, e.g. "may be used for any purpose") is material believed to be out of copyright, either because of expiration of the original copyright, or because the material has been explicitly released into the public domain by its creator(s).
Note that inalienable moral rights and other restrictions may still apply in some countries for some uses.
It is common for publishers to take public domain works and republish them under their own copyright. This may be legal, but it does not affect the public domain status of the original image. If you tag the image with its origin (where you got it and where it came from originally) and the name of the creator, this can help us if a dispute with such a publisher arises later

Following a search on Wikimedia Commons for "green man" I selected the 2 images on this page (one is at the top).

Russel Wills [CC-BY-SA-2.0 (www.creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

-- Marge