There's an awful lot of food set out for an alley containing a dozen visible dead rats. I think I'd replace the food with some crates and trash. You could also grunge it up some—make it look real dirty.
Check out http://www.cgtextures.com/content.ph...ame=blendmodes for a tutorial on how to use Photoshop's blendmodes to apply textures. The Darkening blendmodes one is particularly useful for grunges. And they conveniently have lots of free textures on that site for your use.