We need more dangerous mobs, (unrelated to pumpkins, already too many of those planned) in the spooky dimension. Otherwise the dimension would be too easy.

• Maybe wights in the barrows biome? (Like in the lord of the rings books)

Wights*, not wraiths

Endermen should spawn there, as they can spawn in any Dimension.
Other ideas:

• Headless Horsemen (headless zombies riding the unused Zombie Horse from Vanilla)
• Vampire Bats (bats that hurt you)

• Ogres (basic melee mob, larger and stronger than Zombies, can spawn holding a Club, a unique weapon with a very slow, but very damaging attack)