My only critique would be the "fog" farther down the hall shifts colors rather abruptly instead of being a smooth gradient transition. I also personally feel that the end of the hall is lacking in a little color or detail, but that's probably more of a personal preference than anything.
I wasted ages f*cking with that fog, its saturation, color, density, blah, blah, blah. Tried hand-painting it, tried using a Z-depth pass on the base render as a mask for the fog... Finally, I decided I should just leave it alone, and maybe the solution would magically appear to me later. I may just do a version that fades to black in the distance, or something.
Thanks for the crits, I'll leave it for a bit and then get back to it...lots of aspects need improvement ( I don't like the floor, either). The pipes are 3D (or some are), but they're super quick and easy to do.