Jonathon suggested some woodland-themed elven undead on the post about non-human undead. One kills people to fertilize an unholy grove, the other is a spirit that animates plants. I was kind of thinking "forest theme", too, only I was going to go with something anti-forest; my elven undead would destroy things elves love, in much the same way that my dwarven undead destroy underground environments.
For elven corporeal undead, I propose: grove ravagers. Withered-looking elf corpses with ogre strength. They head towards the nearest woodland when they rise from the grave and begin tearing trees out of the ground, roots and all; they can use an uprooted tree as an enormous maul, doing at least 1+2 damage (more if you aren't using 1d6 for all weapons.)
For the non-corporeal elven undead: blight spirits. They cause plant life to wither within a circle 10 yards across per hit die. If an area is blighted by several spirits, they pool their hit dice to determine the size of the area. They attack intruders, draining life as a wraith; any elves slain by a blight spirit becomes a half-strength blight spirit that infects the same area.
Of course, as porphyre77 noted, the AD&D banshee is supposed to be a particular kind of elven spirit. You could certainly mix it up, perhaps having two tables of random elven undead to decide how an elf slain by a wight or wraith will rise to haunt the living.