This texture is set to world, which makes it obvious that you vertex manipulated it to an angle because the texture is pointing in that direction. I would change the setting to face then rotate/resize it to line it up with the rest. This way the texture will point upwards instead of 45 degrees to the right.

There's a trim on the other side and the wall is symmetrical, so why not have the trim here too?

Now, you've got some serious connectivity issues that would hamper this map severely in dm. I always find it better to get the connectivity down first before working on the big details like lighting and such, because the number of passageways in and out can affect how much r_speeds you have to work with. Because I always want to go overboard with connectivity, I've whipped up some suggestions to improve the flow of this map.

Knock out this wall and make it a doorway to another hall section

Rip the ceiling off this hallway, make a nice sized ledge off of the left wall, and make a walkway over the existing hall. Connect the left end of this hallway to the doorway from before. The other two exits will be the next two pics

punch a hole in this wall for a doorway, but leave the rest. build a staircase behind the wall, and then have the walkway from before connect to this stairway via a small hallway or something

create a second level above this area that circles around the sky area. connect this area to the other ledge in the second picture, but be sure to have a visblocker between the rooms to keep r_speeds down

fill the pipe area with water. since it's a big dead end with one exit i would suggest throwing in a big gun to make it worth going to. make a doorway off the walkway and build a staircase up to the red door. raise the red door and connect the hallway to the walkway. extend a section of that hall to make a stairway that connects to the new second level area

ta da! its all connected, perhaps too much so, but that's just me jumping off the deep end. hopefully this will help you to come up with better ideas than my quick and crappy one! this map has promise, as it looks rather nice and could have good gameplay, so keep it up