Google Custom Search Engine - Free Images
I found a custom search engine for free images created by Janetta Garton:
http://www.google.com/coop/cse?cx=003304322100184285364%3Azyvxtlvb3gm
I thought it may be helpful. The sites that are searched are: http://commons.wikimedia.org http://www.flickr.com/creativecommons/* http://www.pdphoto.org/* http://yotophoto.com/*