Pretty much what the title says. I think it would be cool if bleeding caused a sparse, temporary blood trail to form from the person bleeding out.
If they've started bleeding this life you could also stain their model wherever they were shot with a bit of blood/redness that stays around after they're healed. Could just be a simple overlay.
Would be really neat to have this kind of battle damage shown in general - even simplistically. Explosions, for example, could cover people in soot for a bit. Bullet holes when not healed, etc.