well, which kind of con?
generally i personally like it if not all the colors of the rainbow are in the design but it has a nice colortheme.
thinking about the shirts i own, i like pictures with a little joke in it, maybe a pun. it doesn´t have to be recogniced by everyone.
fine and well done silouhettes can be quite cool, or a fandom in another art style. (like expressionismus, art nouveau, e.t.c.)
oh, and bunnies.
it is hard to avoid bunnies. they are nice.
ohh, how about the mane six as bunnies??