Seeing this in game gave me the idea, I think it might look kinda cool.
War Paint Vanity.
To be worn in the vanity helmet slot, when equipped would render our equipped helmet invisible maybe? or if it can be seen clear enough with helmet equipped, there would be no need for invisible.
Could have many different designs to choose from, maybe even a new vanity layer completely? for war paint and tattoos.
I dunno if it would work, just throwing it out here!