Hey, I don't have any control over what kinds of merchandise CafePress offers. If you know of a print-on-demand shop with a better selection, feel free to point it out (or set up a competing shop-- my feelings won't be hurt!)
Regarding the new t-shirt ideas, the semester just started here and I'm not in a position to commit to developing new artwork, but if someone else has an image they want me to slap onto all the possible merchandise in the shop, I'd be happy to do that.
(Regarding the MR logo on the back... it would cost $3 extra per item. If you really want it, I'll set up variations on products that have it. CP doesn't support printing on the back of dark t-shirts, though.)