strange, I don't think the game would be doing that, although if you create a custom opponent, I could see how it would happen. I don't know anything about changing the texture of the planet, so other than asking someone who makes mods, might need to create a custom race to do that.

Yes its possible to play humans from a planet other than earth, theres the Altarians through some strange quirk of parallel evolution created through the unconsciousness of a sleeping god-like bieng (so goes the storyline, not sure where the storyline is though), and the LentzLandians minor race which could well be a human splinter group.