Hey i here party town also stole you artwork, we're working to have them shut down as we speak! We've written to nintendo dreamworks disney and many more for this blatant art theft. Please join the war on art theft!
Its a double steal then, they stole the artwork which is copyrighted to you and the character which is copyrighted to Hasbro. So the only people who can use this piece of art without permission is your or Hasbro, not party town.
Its especially illegal because they are making money off of it. I heard there is a special report to facebook you can make that is taken more serious than normal ones but it will only get yours taken off and no one else's. Maybe you should just tell Hasbro about the art theft considering the only ones here with enough money to sue is the big companies.
I'm sorry you were stolen from though, I don't watch MLP but this fan art is really super cute especially the eyes and they stole it! I hope they are taken down soon until then you should maybe put water marks or ( c ) Miss-Glitter on top or beside your art. It might help some but, maybe not considering they are stealing stuff even with copyright. I hope you get back what is yours <3