There's one more enemy type coming after that. It has the same model for now, but very different behavior ;)
One item on my task list is to experiment with decals to add variation to walls. At one point, I tried differently colored wall "themes" used for certain parts of the level to add variation and help with navigation, but I never got it to look good enough, so I removed it.
The isolated and claustrophobic feel is sort of intentional. I haven't really made up my mind about where the maze is located but space is one option. Now that there are no windows, I don't have to choose :)