Bōsōzoku is an artistic style from Japan modeled after that country's motorcycle gangs -- or at least the aesthetic norms associated with them. It's found in many different media, from clothing to graphic design. The classic anime movie Akira can be considered a reflection of bōsōzoku.
The style is particularly prominent among car mod hobbyists. Pink Tentacle has a gallery of cars that express the beauty of bōsōzoku.