User blog comment:Wolfishtail/Races and sides in the civil war/@comment-5469467-20130517070733

I would assume that the Dunmer and Argonians would be against the Stormcloaks for the way they're treated (just look at the conditions in Windhelm). Not sure if they'd go so far as to actively support the Emprire, but it's possible.

The Altmer would probably support the Empire to some extent, even if just to put a stop to the heretical Stormcloaks.

Judging by a conversation the player can overhear, the Khajiiit would be neutral and just trade with both sides for maximum profit.

No clue about the Bosmer, though. I would probably say Empire, just because of the Stormcloaks having a dislike for Mer.