Hmm, I tried your mission pack. Maybe a bit too much lava for me.
You should experiment more with asymmetrical designs and lighting contrasts. Pyrite Station, in particular, felt very bright and symmetrical.
(Yes, I know I'm being a hypocrite, but in my later levels, I came to the conclusion that symmetry is quite boring to play in unless it's a multiplayer level. Even if a level is somewhat symmetrical by having a 90-degree bend in it somewhere, it's better than having it be all/nearly symmetrical. At the very least, it makes me want to explore side corridors, instead of presuming that it must invariably lead to a copy of the same robot configuration and architecture).