[@Dark Cloud]

No limit on which races can exist. One dude had vampires. Someone else had horrific mutants with claws and teeth that did not resemble humans at all.

However, your colony [i]was [/i]founded by humans from Earth, so you'll either need humans to be a continuing population and the others as aliens, or create a story in which your humans are transformed into the elves/ogres. Basically, you just need to explain how you got from a colony ship full of regular humans, to a world with elves and ogres.