I had some questions about free graphics and what can and can't be copied, so I found this great site: http://www.princetonol.com/groups/iad/links/clipart.html. It lists websites for teachers of graphics that can be copied and used, and it's put out by Princeton so it's reliable. I was amazed at how many graphic sites we can have access to and use! I also loved the categories- for example there's a link devoted to students who are learning English as a second language. I hope this helps provide some graphic options for you!
Decker, Judy and Ken Rohrer. Incredible Clip Art and Images. 11 Oct. 2008 <http://www.princetonol.com/groups/iad/links/clipart.html>.