I used to have the coolest tire caps for my old bike. They were just a pair of dice, but at least 95% more awesome than the standard caps that came on the bike (the bike store also had similarly cool skull-shaped caps, but those seemed like they'd be tempting fate). If I hadn't lost the dice caps in a move, I'd definitely be using them on my new bike: a pearl-pink retro cruiser with white pinstriping!

So, I know that you can buy dice tire caps from some bike shops, if they carry them.

But if you have dice and some common equipment around, why not try making your own dice tire valve caps with this tutorial by Instructables user Supersaddy? It's a very simple procedure, even easier if you own a drill press: clamp down a die, drill a hole in it that's big enough to allow for insertion of the valve cap, glue the valve cap into the hole, let them dry... and ride off into the sunset with your rockin' new tire caps. You've got style, my friend.

However, be aware that there are two nearly identical tutorials for dice tire caps on Instructables. The other one recommends using Gorilla Glue, but Gorilla Glue may be inappropriate for the project, because it expands as it dries. That means that it can push the valve cap out of the hole that was drilled for it.