Marshall - 8:54 pm on Feb 28, 2012 (gmt 0)
I think your best bet is to watermark images with your domain name and hope that people share them everywhere they can.
I do that now and it has funny results some times. I see G using the right product picture but from my ecommerce sites for other sites in their Google Products. Kind of funny when you are looking at the details of Site A, but the image has the web address of Site B.