I don't believe that weapons currently get blood splatter, though armor does. I'm hoping that there could be a system similar to the armor blood splatter that could be transferred over to weapons that bleed a person- or headshots with various other melee weapons that would reasonably cause the person to bust a lip or nose and get blood on said weapon.
I'm unsure how cleaning the weapon would be implemented in addition to this, perhaps just a 'clean [blank]' command where you get a command message along the lines of 'You whip out a rag, quickly wiping grime and blood off of [item]'?
I think this would add a lot of badassery to characters, though not exactly something that's needed.