I could do skaven and/or vampires.
Separate skaven clans or mixed?
The four kinds of vampire could be separate night creature types in the next release i.e Necrarchs build towers with undead armies but Lahmians infiltrate towns and nobility (vampire cults confirmed in next release).
since i'm a vampire fan i'm drooling at the idea of them walking around (i'm already working on them, my actual progression on them:
i'm working on standard(Von Carstein) structure for vampires (NONPLAYABLE RIGHT NOW) with their own minions:
Vampires - an humanoid that feel no pain nor fear and that his/her only weakness is dismemberment of decapitation
Skeletons - Nonlearning minions
Zombies(pets) - they're just cannon fodder
Ghoul - bigger than humans, poisoned claws that cause suffucation and dizzyness
Wrathguard - Elite Skeletons with buildt in full armor and weapon (to represent own cursed items and weapons) they wont use any other equipment
Vargulf - Walking nightmare, very fast , very deadly and he is even harder to kill than a vampire his fangs are harder than steel
Ghosts, etc - kinda trying create an ethereal attribute
later i planned to add more kinds of vampires (Necrarchs with black magic attacks, Lahmians cause nearby creatures to drop their guard thanks a syndrome emitted, and at least the followers of Aborash who can kill a dragon with their superior martial skills)
that was my project but if you want to take over feel free, i'll keep working on dwarves, right now i'm adding the kraka-drakk slayers