Here's a revised version showing before/after this round. Added darker shadows at the base of each step, fixed the lower floor shadow, and added a faint highlight along the exposed edge of each step. I also altered how I was doing shadows so the layers aren't blowing up some of the colors in the stair texture.

I think this looks quite a bit better. Thoughts?
Click image for larger version. 

Name:	StairTestAB.png 
Views:	365 
Size:	377.2 KB 
ID:	53578