It's a really nice start, but I'd suggest you try these:
Make the walls and roof a different texture to your floor texture. If you need textures, google Mayang Textures... you'll find millions.
I'd also try and give your floor tiles a bit of variety..use a dodge and burn just make em all a little bit differnt to each other.
When you use the bevel and emboss command, never go for the default highlight option, either bring the opacity down or use the colour picker to get a hue closer to the 'main' colour rather than the really bright white it gives you by default.