Looks quite good from the picture but mainly the lighting catches my eye. The building is a little flat if you ask me so maybe you should add a few 'decals' (2D images) to make it look more eye catching. Also add some windows aka glass and perhaps some arches? Bits of walls sticking out?
Just look at a wall and think hmm what can I do to make it more interesting so add arches or cables hanging off it...Lights etc...
I am sorry but I am getting to the habit where i'm so lazy I can't download maps...I am a lousy guy because people download my maps and I never repay them
So I am only judging from your pic...That means your map could be better on the inside.