I saw this in another site, I like anything about bikes, and while I'm not really a 'chopper guy,' I do like a well-executed bike.
Here's a cool graphic that would look good on a t-shirt. You can go to an office supply store and get iron-on transfer sheets that you can print on your home...
If you grew of-age in the 1960's when Easy Rider hit, and the popularity of choppers took-off, you were familiar with these guys. Here's a great ad, real late 1960's/1970's flavor to it, dig the beehive on the lady!