There’s a thing that some French riders do, and I think it’s cool, so i’ve done it. I’ve got a little Limousin sticker from the tourist office and stuck it on my seat post. When you do big races, it tells the other riders where you’re from. I’ve seen riders from lots of regions stickered up in the same way.
I think it’d be a useful thing to do for categories in MTB (VTT) racing. It would help you know who you’re battling against when cats get mixed up. All it needs is a little splash of colour down the back of the seatpost….. and it’s so cool 😉