ah, so that's what took you so long to submit this one, 'cause you vectored the scan XD
Anyway, I think the perspective looks fine, although I think usually the ceiling and walls should be different colours (or at least give the ceiling a different texture), just to differentiate it. Also, rim of the window, since the two parts are at different angles, the shading should be different (er, I'm not sure if you know what I mean ^^;; ). Did you use a texture on the walls? it looks like there's a texture to them....