I think those are looking pretty good. I like your stairs and the wall->fade to black. Couple of suggestions:

1) Might consider "dampening down" the floor texture just a bit. It's very repetitive and contrasty and it hurts the eyes a bit. You used a photographic texture for the walls. Got anything similar you could use for the floors?
2) Those doors are *crazy* white against the darkness of the frame. Maybe drop them back to a light grey? Or, even better, consider a light wooden texture of some kind? If you do that I'd suggest putting them more into scale (thickness, width) because right now they're sort of at "abstract architectural symbol" scale. Also, several of the doors on the last map seem to need the wall cut away around them...a couple seem okay but.

Now all you need is some grunge and "dungeon dressing"! Nice work on these. Have some rep! (edit: eh, okay, after I spread it around a bit more)
M