I do sympathize and agree with WandW about the DMCA take down if possible. Generally most sites will comply within a timely manner if notified.

If you contact the publisher with proof it's possible they will remove the product from the market place. That said, have you always used only your products to promote your work? No hair or clothing from another vendor, or pose? No background or python script to create the scene, or 3rd party CGI program to render? I'm not siding on the person who did this, obvious plagiarism. There's no defense for blatently using someone else's work without permission or license.

On a side note, there are several interesting TED talks about copyright math.

http://blog.ted.com/2012/03/20/the-numbers-behind-the-copyright-math/

The dust settled, thinking "what a fine home, at least for now" not realizing that doom would soon be coming in the form of a vacuum cleaner.