If the Lich King or his minions killes someone and the lich king takes their soul what does it matter what race or class they were they're his minion now.  Then if they break free they're them old selves just with new found, evil powers.  There are more suitable races like humans and dwarves but any race could be one.

Table:
                        Hoard
Orcs-Could work with their bezerking and killing rage
Trolls- same as orks just more spell classes
Tauren-Doesn't make as much sense but if they were cleanseing the land when killed by a lich then had their souls taken could be plausible.
Undead-Well their already dead so only a soul to steal ,with the whole controling thing its only minions so i dont see why undead cant control mindless undead.
Blood Elves-This has proof the Banshee Queen her self had this happen to her.  Her soul was stolen then she broke free and now hates them.
                          Alliance
Human- Arthas enouph said
Dwarves- like Humans but shorter but plausible
Night Elves-Like Tauren may be tryin to clense land when soul is stolen.
Gnomes- least pictureable(if thats a word) of the alliance but may happen.
Draenei-This is also difficult to see because draenei are of a peaceful nature and follow the way of the light not the nether.