Creative Commons is "a global nonprofit organization that enables sharing and reuse of creativity and knowledge through the provision of free legal tools". Creative Commons provides a number of different open licenses that rightsholders may select for their works. When a work is made available under a Creative Commons license, any user in the world has permission to use the work, for free, so long as they follow the terms of the license.
What is Creative Commons? by Victor Grigas (Wikimedia Foundation) is licensed under Creative Commons Attribution-Share Alike 3.0 Unported
There are special requirements for using clip art and stock images in APA Style papers. See the seventh edition APA Style manuals in the Publication Manual Sections 12.14 to 12.18 and the Concise Guide Section 10.1
Common sources include: