I looked at your art listings. Who is the seller that is copying your art? I suggest you start putting a Watermark on your photo. The sad thing about the art world is that because there are literally millions of artists today, the chances of either having your art copied or having another artist come up with the exact same idea as yours are very high. Having totally original ideas that no one else has done is very hard to do, simply because with the millions of other artists out there, someone is bound to copy or paint something very similar to yours. I've seen several artists, lately, who have such similar paint styles, it's almost hard to believe they're different artists. And of course you have some overseas sellers who don't care about copyrights, and will print and sell your art as much as they like. Even if you stop them from doing it on eBay, chances are, they probably have another online store set up to sell it, and it would be hard to track them all down. Even the most famous artists out there have their work copied. Unfortunately, there is only so much you can do. Use a Watermark in your photos to make it more difficult for anyone to Copy and Save your art with the intentions to Photoshop it. And if it worries you that much, talk to a lawyer about what you can do to seek any damages/profits the thieves have made.
