Wait, this thread is almost 3 years old and Nightmare still don't have a gargoyle? XD
C'mon now, a creepyass mansion like that must have a stoned bat hanging around somewhere.
But other then that... I think almost all well known creatures of the night are present. We got zombies, skeletons, witches, vampires, demons, dolls, ghosts, werewolves, dragons, Cthulu, scarecrows, clowns etc. etc. Aside from the gargoyle I don't think there's any 'must-have' left.
I better go 'n play a Castlevania to see if I forgot any