Establish a few tribes you want to work with, then go from there . . . to be quite honest, forcing Elves to be the forest-dwellers is kind of ridiculous . . . we think of elves as being in the forest because our worldview includes Tolkien and all of the rest of high fantasy's writers who shoved elves into the Hippies with Pointed Ears camp. While that could be... okay... I think a race which has good Dex, a low Con, skills at Listen, Search, and Spot, and low-light vision make for some really great nightstalkers. But hey, maybe I just missed something which would require the elves to sit in tree forts.
I would actually probably use the Race as Archetype concept I've brought up before; Elves make for great hunter/stalkers, Halflings are good for smaller, compact fighters who know how to use an atl-atl, dwarves would serve well as stonemasons, bowyers and arrowhead makers, etc . . . Humans could be your default, but it isn't necessary. Perhaps each tribe has a mixture of individuals (or smaller tribal units form around 'family' lines). Crow may choose the Halfling (a smart, quick little bugger who can fight at distance and has a stealthy tendency alongside their athletic ability) while a Hedgehog or Coyote figure may enjoy the Gnome, who knows what it is to be picked on by the bigger guys, and has developed into a crafty, down-to-earth sort of creature.
But to be honest, I could also see Orcs with Wolf and Elves with Fox... of course, this assumes you're using the pan-Indian diasporic animist religion which became popular after the relocations of the 19th century. Assumptions are bad, right?
Slainte,
-Loonook.