This is definetley one of the stranger Sonic shirts out there.
What is really the 'theme' for this? It looks almost nautical, with wood planks, ropes and blue background. It doesn't seem to be from anything Sonic...however along the rop like an odd type of charm are "cards" with character names and faces. Sonic, Amy, Knuckles and Shadow appear, but not Tails. If you look closely, you can find the Sonic X logos on the sleeves. The wierd wood and ropes don't really contribute to any sort of stylishness for the shirt, so it is rather mysterious.