Modders have added a number of new races for the PC version of previous TES games, so I expect a lot of them to pop up. Some of them even fit with the lore, many of them have abilities and stats that mark them as unique compared to the default races. Some were in the Oblivion, but not marked as playable, e.g. Dremora and Golden Saints.
I only play games on my xbox 360,so I don`t know anything about mods etc I`m afraid.I was kind of thinking about Dark Seducers or Golden Saints as playable races, they are a type of Daedra but they act an look more human I think.They`re excellant melee fighters an pretty good with a bow too,so they`d fit in nicely.Finding a reason to introduce them as playable races wouldn`t be hard either,as Sheogorath is very inpredictable as we all know

it would be just like him to cast them out into the world.