Simple Suggestions:
1. Engine Trails during combat, for the small ships, and maybe when you move a ship (just follow it and disappear on that turn, nothing that sticks around for a few turns). Also if the engines of the larger ships emitted some kind of engine effect or glow, that'd be hot.
2. Some more simple interface sounds and alerts. For ideas and examples, check Birth of the Federation. Before combat actually begins it would give a "Whiiir! Whiiir!" red alert sound for a second and show you a short summary right before hopping to the battle screen. Difference is that BotF had very slight tactical combat; not all fleet battles in GalCiv 2 even have to go to the screen. Another example is just that when you hit buttons or move sliders, there's sounds that let you know something is happen. Also small alert sounds for social events, anomaly findings, so on and so forth. Another good example is Civ 4; when you declare war or vice versa, there's that awesome horn blowing sound. And when there's peace, similar thing.
3. Something to allow launching multiple ships, or setting a star port to "autolaunch when complete", so if a ship is finished, it automatically launches. I'd adore that.
4. Having the light extras actually create a light, rather than just a lit up ball.
5. Show the max pop a planet can support, along with what they have and how fast it's growing.
6. There's certain buttons and sliders in the game that are really dark. My best example are the minimap toggle buttons. I have the Brightness and contrast pretty up when I play, mainly because I can't see those buttons unless I do. However, having it so high makes the actual galactic map look a lot less like space. If you could make those buttons brighter and more highlighted, that'd be awesome.
