These home-made t-shirts at ilovetocreateblog look pretty great, and don’t appear to be too difficult to make.
I especially like the negative Yoda tee on the right, which looks like he might be standing in front of the lights of a spaceship. As usual, these methods could be applied to so many great and iconic geeky franchises. Just pick your favourite character/spaceship/vehicle/insignia and go nuts! Make sure you check out ilovetocreateblog to see how these tees were made.