I think pre-Cata, in lore all player-character Forsaken are Lordaeron undead (correct me if I'm remembering wrong), but since the starter zone has changed to having new undead raised by the Val'kyr under the command of Sylvanas (who, in SoO, shows she has no qualms raising other fallen Horde races into Forsaken), so I think it's safe to say there's plenty of room to be able to consider that PC Forsaken can be just about from any race