An idea I had that could be used for a drug shirt would be to take that 'food guide pyramid' and just replace 'fruits, vegetables, etc, etc' with different classifications of drugs, with pictures of the drugs and paraphenalia they are associated with.
So instead of having 'grains' at the very bottom, you'd have 'hallucinogens' with a picture that has some blotters, shrooms, peyote and what not all sitting together. Or maybe 'stimulants' with some cocaine powder, crack rocks or meth crystal. Could even have 'serving' recommendations on the side. :D