The map looks far to evenly structured. Try to break up the layout, move buildings closer, to each other, add some height levels... right now it looks like a big open field with "something in".
First thing I noticed, though: It's too dark! Even for a night map! Make it 2, 3 times as bright, at least make sure the floor is lit by spotlights ect to make sure the player isn't blind when playing it at day or low contrast!
One last thing (sorry, I wanted to mention the nice looking machinery in the last pic more <:] ) - there already is a map with a very similar theme called dm_mine. It's a decent map although it has a weird layout at places. You might want to know that, although there's room for more than one mine map IMHO.
It's pretty dark if you ask me. Too dark to see much in that first and last shot, so probably too dark for gameplay as well. And I prefer daylight maps just for their mood, for some reason they seem to play 'happier' to me.
Look into 3D skyboxes bytheway, I'm sure you can make that background outside more interesting. :smile:
