I am really enjoying watching your progress. That converted vampire looks great. The necromancer is pretty awesome as well. I like the roughness to his cloak, makes him look quite bedraggled, as a necromancer should!
I haven't used cotton wool mist myself yet, but I think it looks pretty great in the pictures I've seen. I say, why not try it, and if you don't like it you can always take it off.
Side note: the four horsemen of the apocalypse page is one of the most interesting I've read on wikipedia. Can't say I remember much of it, but if you used all the different versions artists have described over the years you'd have a very large unit. Keep up the great work!