[Vicious Love]

... and more vikings. We've been over this, Calistas.

Anyway, if we're just indiscriminately adding in historical and semihistorical human nations, I wouldn't object to seeing something vaguely Polynesian. If Dom 3 ends up having proper naval combat, rather than just submarine combat, this might be extra-fuzzy. In a good way.
Proper, folklore-heavy eastern Europe(Era of your choice) might be nice, if it doesn't overlap BF Ulm too much, and there's always something to be said for India. Furthermore, please make T'ien Ch'i even more ubercool than they are at present. Thanks.

I'd also like to see existing nations changed by the Ascension Wars. For instance(And this is a very particular instance which by no means begins to encapsulate the whole), you'd assume a few predator lizards woulda found their way into the other nations' societies, rather than remaining nothing more than a C'tissian slave race. Especially if certain otherwise feeble nations end up using them as the backbone of their armies on very hard research games.
Ditto regarding humanbred Abysians. We assume they're anatomically compatible and, whether conquerors or conquered, it's safe to assume at least some of them worked their way into the gene pool of the postwar generations, adding a bit of ethnic and possibly cultural diversity to, oh, say... T'ien Ch'i. They'd never have seen that coming.

Lastly, I think it might be both strategically and thematically interesting to have a nation that somehow changes, in significant ways, with the passing of the seasons. No matter how you interpret a suggestion that vague, the results are all sorts of cool rolled into one. Of course, this might just be an expression of my wanting to have terrain and other environmental conditions have more of an impact on gameplay(And style, people, STYLE). Even with a fully equipped Heliophagus on hand, one does not invade Russia in winter.
Other than that, it's all the same to me, so long as you continue avoid generic fantasy and other strains of the dreaded cliche like the plague. Honestly, no orcs.