There's a lot to love about bikes: they help you burn calories, they're good for the environment, and they're exactly twice as cool as unicycles. For a line of tees lovin' them even more, check out Dark Cycle Clothing.
From a Tampa couple heavy into promoting alternative forms of transportation, DC handprints ring-spun non-sweatshop tees with their own clever illustrations, most of which involve all manner of creatures on bikes, making them totally oddball, also the result of a bad bike seat. Cycle-ness includes a dapper badger in a top hat/coat cruising on a Victorian penny-farthing, a vibrant yellow bike wheel (sitting in for a skull) and crossbones, and two pedaling predators: Dinosaur, with a green T-Rex relaxing on a mountain bike, and Shark, with a great white on a fixie, totally increasing his odds of biting it. Non-bike standouts comprise the Raygun Steampunk Blaster, a big Jules Vern-ish laser pistol, the Cassette Monster (an old tape made into a beast with a gaping maw of scary teeth), plus math & science jobs like a black tee printed with the Periodic Table, and one with the entire shirt covered by the number 3.14 etc, called Pi Math Geek -- which comes in sizes up XXL, so it'll likely handle your circumference.
DC also does custom colors on all shirts, and even has a canvas shopping bag with a medical illustration of a big, meaty heart that's anatomically correct -- so clearly, it never tried to ride a lame old unicycle.