I agree that more variety would be nice. Kinda strange that we went from the insane variety and customization of GalCivII to Elemental, which also allows for designing units, but in a much more limited way. The main problem is that you are dealing with living creatures, not ships, so that really impacts what you can do.
Here is what would help, in my opinion:
1) More variety, especially between cultures. If one culture is refined and artful, let their armor reflect that. If another culture is brutish and crude, let their armor reflect that.
2) Give us the ability to add ornamentation to our units. Same thing as GalCivII, really, just small visual touches. So for the refined culture, maybe I can add artful decorations to armor. For the brutish culture, maybe I can add a necklace of bones, spikes, skulls, etc. There needs to be a limit to keep things sane, assuming that too many ornaments will slow down the game, so that people don't make a unit that has 10,000 spikes on it.
3) Allow for variety in like-units. Right now, a squad of guys looks silly to me because they all are clones and move in the same way. Take a look at the difference between Rome: Total War and Medieval: Total War. I loved Rome, but I have a hard time going back to it because of the clone armies. In Medieval, soldiers within a unit have a variety of faces, armor, etc. Allow us to do that in Elemental by selecting several 'variants' for each unit, so that you will see different hairstyles, clothing colors, etc. Or, if we want to have an organized, uniform appearance, we can keep variants to a minimal level.