Along the lines of more NPCs wandering around, I think more ambient messages would be really cool to see. Something similar to the randomized messages that you see in the Mix after the room description, these would be similarly written but would appear randomly in rooms, giving the streets the feeling of being more alive.
A few ideas:
Red
You hear the crack of gunfire in the distance.
A car screeches wildly around the corner and blazes down the road.
A woman screams in the distance.
A group of gangers shove a weak looking shirt to the ground and demand payment for safe passage.
A street fixer calls out in , shaking a tray of ancient looking progias.
Gold
A steady stream of traffic rolls down the roads.
A dirt-covered courier is stopped by a Judge who begins questioning them about their destination and identity.
A WJF AV cruises overhead at a slow, steady pace, kicking up dust and a few chy notes into the air.
Green
Well, I don't spend enough time in Green to have some good ideas, but you get the picture.
