Beholders are probably a given, we already saw dragons.

That beeing said, the graphical fidelity of this game and the requirement of unique animations is going to make this a challenge.

When looking at the screenshots so far tho, im quite impressed with them going with some... i wouldnt say exactly uncommon but more obscure monsters.
Specifically the Wolf like things you see in the goblin screenshots, im fairly sure thats a barghest