It looks good but a bit too simplistic. You have around 6 colours being (grey, light green, dark green, red yellow/bage and dark grey/blue). It reminds me of a tutorial level in one of my 3DS max books which also uses a mental hospital. Maybe try and balance out some of the colours by adding in maybe a rusted out car or…
I think decals would greatly enhance this scene, they are pretty easy to setup in UDK and that way you could add a little more grime to the environment without touching the textures. At the moment, it looks too un-weathered to be abandoned imo. http://www.hourences.com/tutorials-ue3-decals/…