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I'm not very interested in all the trivial details about the appearance and names; the developers will do as they see fit, and they are unlikely to listen to our opinions. We will only be able to evaluate the result later.
Personally, I would like to see a kind of overall dark, nightmarish, graveyard-like, and ominous image for this faction (as has been the tradition), raspy voices, hoarse dialogues, a mournful musical atmosphere à la the third game, and cobwebs instead of curtains – that would be secondary.
There should definitely be a lot of necromancy, a whole lot of necromancy! I can't quite imagine them without all sorts of resurrections and raising of the dead, and it would also be logical – games with death.
And, since this is a new installment in the Heroes series, you could also add a new feature, like the antimorality that was discussed on the Nival forum, or something similar.
Everything else is not very interesting at the moment. I will try it out when it's released (at most, a couple of months).