E1M4:

-Changed ceiling texture in the little starting room to brick instead of that awful gray ceiling lamp texture
-Evened out the lighting in that area and made it more of a room than a hallway
-Changed the ceiling of the "eastern" corridor leading t the computer room with the trap to brick so that it's consistent with the western one
-Slightly re-did the room with the lift and computers, got rid of the pointless switch and walkover linedefs to activate the lift
-Refined the architecture in the room with the imps and barrels, and un-fucked that ugly BROWNHUG staircase nearby
-Fixed the little HOM at the entrance to one of the high-up "window" corridors
-Changed the texture in the rocket launcher/soulsphere secret to marble instead of ash.
-Refined some of the heights and textures in the big circular hub area
-Fixed the textures and architecture in the big STARTAN room with the ledge and the trap activated by the lift
-Redid the weird room next to the blue door leading to the maze (but keep the same overall concept)
-Turned the computer stack back into a swastika
-Made the exit room less cramped and re-texture the little exit alcove
-Darkened the corners of the maze a bit
-Moved the blue door to the entrance of the room with the funny-looking balcony
-Removed the yellow key entirely and made the door leading from the maze to the exit chamber locked on the chamber side.