I made a shirt showing, in my opinion, one of Bitcoin's most important aspects:
https://i.imgur.com/GzN3ecU.jpgThe message is a bit of a double entendre in that bitcoin has no borders, and neither do the letters I used. I feel that a white shirt best showed this in allowing the letters to bleed into the shirt.
this design is visible on my storefront
here along with some other designs like scarves, clocks, stickers, etc.