Ninjas riding bicycles is pretty hard to argue with on the scale of all things cool. A gigantic, life-sized decal of Kate Upton might be better, but no one wants to look like that much a perv. Anyway, back to ninjas on bicycles. This particular decal, based on the ridiculously popular Threadless t-shirt of the same design, is black, 36” x 27” and gets mounted on your wall like every other wall decal. Cheaper, less work and less messy than painting the entire wall—and it looks way cooler.