NADD t-shirts? I think you can take any Picasso painting and you'd have a good starting point.

And being argumentative : you're wrong about the tip jar! Bahahah.

(imho you should put a tiny tip jar button off to the side ... and never, ever, ever refer to it. There's a class of people that still like to express gratitude, and cash is an easy way to do it on the interweb. Why not take advantage of it? :))