A Major Doomworld Concern
Shots 2 and 3 are nice, though the orange lights built flat onto the walls used as supports in shot 2, as well as the door built completely flush against the wall with no doorframe, look wonky to me.
Shot 1 doesn't convince me at all, I'm sorry to say.
For one thing, everything is the same height on top: you've got a completely flat line where the rocks and everything else meet the sky. They don't all need to be 1-sided walls, so you could very effectively turn the rock walls into raised-floor sectors at varying heights, building some nice smoothly-shaped layers (a la SID.WAD or what have you) to give them a more realistic, natural feel.
In addition, the gray concrete overhang on the left just sort of sticks out of the rock with what looks like support textures or something stuck onto the edges of it. Make the entire building stick out from the rock a bit, possibly vertically as well (this should be doable once the rocks to the sides of it have been turned into raised floors), so it actually looks like a building that's been built into the face of the cliff rather than...well, whatever it looks like it is now.
The new shot looks like N5 texture overload, and the floor could use a point of visual interest in the center, possibly something brown (or maybe even tan, depending), to reflect the gray/brown theme from the walls and ceiling. Also, Light Does Not Work That Way(TM).
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