Designing a campaign setting that you've already got partially designed is a fun way of excercising some creativity. Eventually, however, I have to get to the point where I can declare -- "finished!"
Some important details:
* The inhabitants of the Known Lands are descended from travelers from a distant star.
* The Eladrin and the Orcs are genetic redesigns of the human.
* There are no Eladrin, there are the Massalian Elves (or Fair Elves), the High Elves, and the Dark Elves (considered to be peasant folk by the High Elves).
* Orcs are split into different tribes: the Silverfang Tribe, which worships the Wolf spirit; the Hawkfeather Tribe, which worships the Kestrel; The Blacktalon Tribe, which worships the Deinonychus, the Dragon Ochre Tribe, which worships Black Dragons; the Crimson Dragonfang Tribe, which worships Red Dragons; and the Tribe of the Shattered Cross, which are christian. Also included is the tribe of the Burning Blade, and the Tribe of the Smoldering Spear.
* Orc tribes each get a favored class. Like the families in the Great Clans of Rokugan. (Tribe of the Burning Blade = Warlock, Tribe of the Smoldering Spear = Barbarian, Silverfang Tribe = Shaman).
Other races, except human, get a favored class. I'd do humans by nation, if I really wanted to do that. But I think not.
There are other things that are ideas in my head. But those are the greatest so far.