An idea straight out of counter strike, without the inappropriate .gifs.
I expect most of you have played CS and know how sprays work, but the idea is that you'd be able to spray a single-colour version of your outfits logo onto terrain. Warhammer 40k chapter badges being a good example of the kind of thing I mean.
It's nothing game-changing, but I can see it being fun/potentially useful. Fast response outfits could put them somewhere visible to show they've responded, support outfits could tag the walls next to their lodestar to advertise their presence or rampaging murderers could use it to tag their kills etc.