I'm an Arduino fan and a graphic-t fan, so yay let's combine the two! My original idea was to create a more stylized design that played off the Arduino schematic but wasn't necessarily realistic or authentic in terms of its symbolism, but possibly was cooler to look at.
Needless to say I'd screen print the design. My original idea was to use the bleach & stencil method, but there are too many fine lines... I doubt it would work.
Schematic is from the Arduino website and the shirt image is by Flickr user Timtak. Both are Community Commons images.