When in doubt, look at No Mercy 1 & 3, along with Dead Air 1 & 2. Great reference material if you're going for a setting like either of those.
A few other things I noticed looking at your screens more that jumped out at me.
Is light only coming out of the top of the overturned lamp here, or is there a wall/doorway blocking the light that should be coming out of the bottom side of the lampshade?
[Blocked Image: http://img13.imageshack.us/img13/3673/l4dthewire0010.jpg]
The closest street light in this picture looks like it's on, but it looks like there's no light being cast from it.
[Blocked Image: http://img707.imageshack.us/img707/6397/l4dthewire0013.jpg]
For the broken wall, is there a way to overlay brick texture onto the white? You could also consider changing the surface to get across to a wooden plank, which will make it a little more dramatic (at least to people with a mild to severe case of acrophobia). Is this current platform an air vent? If so and you stick with that as your platform, you may want to lower them, as they should line up like they're running along the ceiling of the floor below the one you're entering and make sure they have some structural support. I'm guessing this is a spot for smokers to pull survivors down to the street (my personal favorite in versus maps).
[Blocked Image: http://img704.imageshack.us/img704/5830/l4dthewire0029.jpg]