Alright so first thing is that in some of the images for the Stargate group, the ceiling is in complete darkness. Future lighting does this a lot, and the easiest fix I could see is widening the angle of the lights or adding invisible lights that only illuminate the ceiling.
In the servers, you could add some wires as extra detail and to make them more realistic.
You should also consider empty floor space. Many of the rooms you’ve showed have a ton of space which doesn’t serve a purpose. It makes the build look emptier. If this isn’t intentional, then you might want to either make the rooms smaller or add more to them.
For the reactor, you might want to add small pipes around the structure simply to break up flat surfaces. You could also add some trusses (custom made ones, not the default ones those look bad) onto the support beams for some extra detail.
For the cave area, you should consider adding vertical support columns. Most mining operations either leave columns of rock to support the land above or add supports to prevent a cave-in. Could also be an easy way to squeeze in some lighting to highlight important areas.