I'm not sure if something like this has been suggested (it probably has due to popularity elsewhere), but if it hasn't I'm suggesting it, if it has I'm expressing support for it.
Now there are all ready zombies and skeletons in the game, but what I have is slightly more for the terrifying and haunted biomes they are in, or perhaps this may even apply to FBs or something.
Suggestion 1: If magic is implemented, necromancers. It'd be a lot more !!FUN!! if a siege of goblins came and one of them was a gobby Necromancer, walking by your refuse pile and suddenly bringing back all of your dead dorfs, this could produce horrific thoughts to the past dorfs loved ones as they butcher them from the grave and so on and so forth. Perhaps the demons from Hell would also have something like this going on.
Suggestion 2: A plague or virus symptom that causes berserk behavior to those infected. Dorf A kills FB, FB toxin causes Dorf A to go berserk, Dorf A attacks Dorf B, Dorf B goes berserk, Dorf B attacks Dorf C. Or it could just be something that causes a vomiting blood sympton, bleeding from the eyes, unconsciousness, and then the dorf wakes up as a Zombie Dwarf that moves slowly and so on and so fort.
Those are my two suggestions in very very general detail.