TinEye.com - beta testing visual search engine
 

Here's new software that will help you know where your images end up online. You might want to sign up for the beta of TinEye, it is a visual search engine -- it matches the "thumbprint" of images, instead of filenames.

To see how it works, check out the following:
http://tineye.com/widgets/display/

http://tineye.com/login

They've only indexed a small portion of the Internet at this time (about 500,000 sites) but I think it is growing and is probably a good search tool for artists.