Giving civs more character- Different architecture for each civ
Altarians- Smooth domed buildings, predominately light blue in color, with plenty of arcane symbols down the walls.
Torians- A combination of smooth curves and sharp spires and edges, predominately emerald green.
Arceans- Heavy and bulky looking building, predominately stone-brown and with few aesthetic touches.
Drath- Buildings usually archaic and fortress like with flat rooves, battlements and sometimes towers.
Korx- Largely charmless architecture, with plenty of poorly thought and clashing aesthetic effects.
Drengin- Rusty looking hexagonal structures, reflecting the Drengins real lack of interest in either appearance or design of civilian structures, militery structures should be pristine, manacing looking and painted in black, red and orange colours.
Yor- Industrial looking steel structures, with plenty of purple lights and touches. Should look in-organic and artificial.
Thalan- Huge earthen mounds of varying size (similer to termite mounds). Tiny lights should be visable on the flanks of the mounds to give them a lived in appearance.
Iconions- Pyramidical and studded with arcane symbols down the sides. The buildings should look alien, exotic and arcane.

Needless to say, we'd have a VERY cranky art staff on our hands 

That's from Game Design: Secrets of the Sages.
) Granted, I think full customization of all structures, ships, interface skins, and even diplomatic avatars would be beyond exhilirating (I'm a huge proponent of "species identity" in these games,) but I try to be, above all, pragmatic when it comes to my games -- I'd rather it play like a dream than look like one, if I'm forced to choose, and from what I hear from BoogieBac, CariElf, and FrogBoy, they're thinking along those lines too. That being said, what little I've seen so far looks pretty dreamy, so I have little to complain about in that department. (And an aside to BoogieBac, I still can't wait to see those diplomatic animations!)