Hi,
I'm new here, so please tell me if I break rules or something (I read the rules, but I'm sure there are some unwritten conventions I may not be aware of).
Your roof looked more like a floor, so I thought I may be able to help. I think the shading model I've drawn is ok, if not, please correct me. The walls are not properly shaded, maybe someone else will get it better - I'd actually like to see it. I tried to improve the door's and window's perspecitive, but I'm not sure if it's right, too.
It's not a very good redraw, but I hope it'll be helpful - I mostly meant to make the roof look more 3d, and didn't make it smooth with dithering or anything.
I think that the second (mine) pallete is cooler, but I don't know if you're gonna like it or if it will fit your purpose.