what you should do, to make sure no one cheats....is over the original...put something like "original" over it in big letters so no one can directly rip it....maybe make the letters an overylay so you can still see the pic....
It's easy to see if somebody rips it. Just set it over the original in Photoshop and set the layer to difference. If it's black, it's the same pic. And where's the love (or acknowledgement) for my copy?
Here's how mine stands up to the difference test.
[img]http://www.xbox-connection.com/hostedimages/l7diff.jpg[/img]