While this would be a cosmetic change, I think it would be nice to have that the stations upgrade/expand visually when you upgrade their level.

I know significant model change for 10 levels, for all stations might be huge workload/test wise, but I think even small cosmetic change per level (e.g. additional solar panel, additional module/bulkhead, additional rotation ring for habitat) would be great.

That way you could notice the difference between level 1 and level 10 station.