Game Interface menu allows you to change the names of the races. It's pretty useless though because those changes only take place AFTER loading the map. For example: the first time you play the map, you'll still see human, orc, undead, ne, and if the next map happens to be a melee map, you'll be playing as zerg, terran, protoss or xel'naga.
Adding or removing races is not at all possible.