Just a few simple ideas just to add a little of the human element/back story to nation space. These ideas are strictly aesthetic but, in my opinion they might add a sense of immersion as they would give a visual sense of the differences between the nations.

UIT...
The UIT are a strictly space based & profit driven people, yet for the most part their stations no larger than those of the other nations. It just seems they should have significantly larger...(and flashier)...stations. Maybe even city sized stations to accommodate the larger population.

Itani...
The peace loving, philosophical artistic race. I imagine in game this is hard to portray, but there are some ways it could be done. The thing that immediately comes to mind is artistic talent. Perhaps they could have a station or stations on or in asteroids which have been "carved" into likenesses of Eo or other great leaders of their past or with carved scenes. Or they could just have roids carved as statues out in space near stations.

Serco...
The warrior tech heads...VO's very own answer to what happens when Klingons and the Borg have pissed off babies! Very competitive and aggressive in their nature but, nothing in their space really reflects this. Perhaps they could have their own tubes, or as they are a combative society maybe transparent "combat spheres" where they and those who would challenge them could fight for glory.

Just ideas to help visually separate the three nations. Naturally other ideas are cool too.

Absolutely agree on UIT stations, i can't bring myself to belive they are housing whole civilization as is.

I just figure the majority of the UIT population live on other, nicer, stations elsewhere. Nobody wants to live next to, much less in, the spatial equivalent of the local industrial park.

Have to disagree about the aesthetic differences between stations; there are differences, just not overt ones. UIT stations tend to be more haphazardly put together with function trumping form; Serco stations are blocky and solid; Itani stations are spread out with lots of those panely things. There are color differences as well but mostly in the highlights.

Not to say more distinctive looking stations wouldn't be welcome, especially the capital stations, but overall, considering the shared technological basis of all three nations, I find the current station designs sufficient.

Slightly off topic. How about putting large stations as unreachable objects into the background?
They could even just be prerendered like planets, so they wouldn't have a large performance impact.

Homeworld had a level a bit like that and looked pretty cool.