I've only been toying around the theme a little but I think I can give you _some_ pointers. First, I'd certainly make a magically versatile pretender so that you can rely on some good summons (behemoths, yay!) when all the living dudes have deceased from your kingdom. You're going to run out of living troops very soon and you really can't be relying on masses of undead, either (you don't get bucketloads of people as with ermor). In other words, I'd make as many dryads/panic apostates (whichever you prefer, pans might be better since you won't have other good uses for the money, anyway - black centaurs are bit too expensive to my tastes) as I can and have them research to get to those good summons. I'd steer clear of Vine Ogres here, however. They're good summons but I really don't want my 320/350gp (depending on theme) Pans to sit home summoning.
Btw, has anyone managed to figure out how the unholy levels contribute to the kind of stuff you can reanimate. I assume you need 3 levels to reanimate carrion elephants and probably 4 for that ettin dude. But other than that, I noticed no major difference in quantity. I thus suppose that it's rather safe to assume that carrion centaurs are the way to go if you want lots of small stuff. Those movement 20+ beasts can also attack the enemy right off the bat with the quickening spells (I laughed my *** off at the first battle - "heck, never thought the dead guys could go _that_ fast"). Ok, you might find this weird but you should actually consider the undead guys your elite troops
. Mandragoras are probably some of the most underappreciated units in the game. You should thus consider using some fodder to protect them. Casting swarm in the first round can really prolong the (un-)life span of your troops. Spirit mastery is another spell you should seriously consider. You get 15 fodder for just 4 gems, best bang for the buck as far as summoning spells go. Ghosts/shades are ok too but more gem-intensive.
PS. I know I'll be playing against you in that game but this is what I think is the best way to play the theme atm, honest. :>