Gnome or Dark Elf Necromancer?

[Neric]

Dark Elf for the looks without a doubt. Iksar for the regeneration.

[Cen]

Hide is a great racial, but worthless on Necromancers.

Its amazing to be able to AFK safely and indefinitely. However hide kills your pet and necromancers automatically get a stronger tool to AFK with that doesn't kill their pet. Also it works on Undead. The only downside is you can't Med with it but whatever. As someone already stated, there is essentially iksar and non iksar necromancer

[Aaramis]

On a class that can snare, fear, charm, root, DoT, nuke, invis, ItU, summon a pet, summon corpses, rez, lifetap, health transfer, mana transfer, breathe underwater, levitate, and probably a bunch more things I can't think of, does race really matter?

Just roll and conquer the world.