Nothing I have missed in practice, and not much I foresee missing much, either, but here's the monster I liked to see, though most of them have no priority.
- Formians. I need some Borg Hive like non-evil beasties bend on expanding their worlds. I have actually statted them as an "exercise" for using the monster guidelines. I suppose I should post them in House Rules.
- Delver. (Elite Brute?) Liked that one, though I only ever used it as a shape shifter form for my Druid.
- Animals. Lots of animals. I think we'll see more of them eventually, but I somewhat miss the 3E MM appendix with animals.
I would like to see a return of Master of the Wilds "Legendary" animals - as Paragon Tier equivalents of regular animals. They should be magical beasts, not mere animals, though. They represent the awakened and paragon versions of their species.
- Shrieker done right. He should not just stand around there! Maybe a Controller (Leader)?
And I also liked the Phantom Fungus, despite the totally metagame reason for his existence. (Maybe a Lurker?)
- Xill. There must be some race that infests other creatures with his eggs! Also a great opportunity to use the cool disease rules. Probably a Lurker (can turn insubstantial)
It's funny that we share 3 monsters we want to see again!
There are probably others, but these stand out.