I tend to dislike the enemy race "garbage" (in my mind, that's what it is), and threw it out. Similar to Eberron, though it was the same in my 2nd edition short-lived games in an unformed world. Just seems a bit... "racist"... that all the enemy races are primitive tribal rather deformed monsters (green skin with huge tusks, or short with giant noses and ears, among other monstrous features) while the player races are beautiful smooth skinned (mostly pale, some with darker) living in civilized cities and wood/stone structures. That part never sat right in my mind. So, I changed it for my world.
Orcs (there are no half-orcs, nor half-elves) are black-skinned with eyes and hair the shades of flame to reflect their volcanic and fiery homeland. Orcs originally descended from elves, and orcs can still be born of two elven parents if they spend over 100 years within that area. It is speculated that if two orcs could live long enough and reproduce, an elf would be born. However, orcs don't live long enough to be able to find out.Also, within one of the volcanoes lies the entrance to the Plane of Fire.
Elves are the offspring of fey and my race of humanoid plants. Due to this ancestry, they are greatly tied to the environment. Similar to the above with orcs, an elf born from two high elves who spent 100 years within the perpetual darkness of the Shadowlands (a land above ground but with a portal to the Plane of Shadow, which makes the surrounding lands in eternal night), would give birth to my world's version of the drow. None know what would happen in the dwarven mountains, or on the water, and none have dared try.
Gnomes are no longer the happy-go-lucky trickster illusionists that is typical in most fantasy and D&D. They are instead warlike, and live in regimented society. All gnomes must spend 10 years in the national military. There are still 2 subraces of gnomes, living in the same nation, but are different. The one are still tinkerers, and make up the craftsmen and farmers, while the other is war-like. Think the Spartans from 300, and add in steampunk elements (their homeland houses a portal to the Plane of Water, so there's water aplenty for steam power). They also created the Warforged, and are excellent seafarers.
Gnolls aren't demonic slavers of the deserts. They are rather peaceful giant bee keepers who travel the land selling the honey collected from these bees. It is sweeter, and has a mood booster effect that makes the eater happy and relaxed.
Goblinoids (goblins, hobgoblins, and bugbears) live in a mist shrouded country between the blazing hellscape of the orcs and the water-sodden lands of the gnomes. Goblins and hobgoblins have human skin tones, though goblins are still small. Bugbears aren't born, and are sterile at that. Instead, they are created by 6 goblins and a hobgoblin, where 6 of them transfer their life essence into the 7th. The recipient isn't chosen, and no one knows who gets the power until after the ritual. At the end, the ones that didn't get the power collapse dead. Bugbears are excessively rare unless in a time of great strife (such as wars).
Humans are practically extinct, being my world's only "enemy race", having attempted to kill the "lesser races" but were instead brought to near eradication. They did, however, kill the halflings. There are still small pockets of humans, but the more unsavory of the other races who come across these pockets enslave the humans, whereas most of the other races kill them on sight.
Aasimar, Tieflings, and Genasi are "templates" added onto a "base race". They get the abilities of the planetouched, but appear as a different race. So, there are aasimar who look like orcs, tiefling elves, water genasi gnomes, etc. The only way someone can appear as a halfling is by being one of these. So while the true halfling is extinct, there are some planetouched with the physical appearance of halflings that still exist.
I also have an empire of Sahuagin in the ocean, with a small island chain (I say small, but it's about the size of the state of Georgia + South Carolina) above ground where they initiate trade with other races, when they don't feel like sinking their vessels.