Hashut’s Blessing:
Biker boots would be a must. A tattoo that they all have somewhere too 
Instead of ammo-belts, give them dagger belts crossing over their shoulders…
Baggronor:
Goggles!!!
Perhaps check the 40k speed freeks and gorka morka stuff for inspiration?
black hammer:
I agree with baggronor, goggles are a must! You should also add some kind of bandanas and leather jackets.