Very nice. One big issue(for me anyway) is that the crumbling walls don't match the rest of the style, particularly with the drop shadow. The drop shadow makes them appear to float above the floor. One way to get around this is to use an outer glow type effect to have the shadow on all sides, and then perhaps a bit more on the side with no light on a separate layer. Also, I would ditch the existing texture (the GIMP moon footprint) and use the same colors as your outer walls(using a layer mask where you want it to show through. As it is, it breaks the consistency of style with the watercolor hand brushed outer walls and floor for me.