Well, at least your work is here where most people will come and they will see who the artist really is. I doubt this guy will get many people to visit his site of stolen goods since the poser forums are very closely connected and people have access to the true artists gallerys. As for shutting this person down contact his website provider ad file an official complaint with them, The may have a terms of service provision about stealing copyright materials. Include in the e mail to his service provider the website of your work and a letter from renderosity vouching that you are indeed a member here and that your work has been witnessed as being yours.