I went through the topic, and a lot of the art shown remains unposted... So since I already took the screencaps and posted them for Minisgallery, here they all are! I will also repost a few where I have bigger/better pics than the ones posted in the first post.
(Except Flumphs... someone mentioned them in this topic, but I did not see them... if anyone has that art, please post it!)
Beholder
A very very filthy Otyugh!
Zombies - specifically, the same ones we had in 2014, regular humanoid Zombie (Human and Dragonborn depicted), Ogre Zombie and Beholder Zombie!
Flesh Golem in a classic "It's ALIVEEEEE!!!" pose.
Spectre - they do mention their sunlight aversion while this pic is shown, hence why I think this is not the Ghost.
Unicorn
Blue Dragon
Tarrasque
All sorts of animals
Bone Naga and its master
Ancient Red Dragon
Ancient Green Dragon
Now this, I am not sure about. I hope it might be finally art for the Lacedon - aquatic Ghouls - but it could be a Scrag too. Or some other watery undead?
Lamiae (female and male, lion-bodied variety) attacking a Copper Dragonborn on a Camel. Oddly, the Dragonborn still has the older style Copper horns.
Magmin setting fire to a library.
Oni/Ogre Mage doing its best Gowron impression!
Hill Giants going shopping.
-"Goblins!"
-"They are fey now?!?"
-"They are fey now."
The stream mentioned more NPC stat blocks for entertainers, acrobats, musicians. I am guessing this is the art for them.
Frost Giants. Guess they brought back the 4E ice axes? Those won't be useful on raids to arid lands, just saying...
Bandits! Love the art, a lot more varied than the old one with many species. And looks like we will get Bandit spellcasters too.
They mentioned Warlocks, my guess is this is the Warlock of the Great Old One (those worms are a dead giveaway of a Kyuss worshiper) fighting a Warlock of the Fiend.
Most likely the Assassin. Poisoned bolt and all.
War Priest, or healer, maybe? Some cleric NPCs.
The other two Vampire art pieces were posted, here is the third, looking more traditional Dracula-style.
Gnolls! Who are now fiends, and seem to come in all the colors of the rainbow. Is the one on the right a green Gnoll Mummy?
From the bone flail, I am guessing the one in the center is the Flind. If so, that is a mighty obscure Baldur's Gate 1 reference - Flinds had purple fur with a red mane in that game!
Remorhaz! And, erm, Penguin? More like lunch.
Probably a new stat block will be added for Unicorn Foals?
Skeletons, Skeletons everywhere! Including the Warhorse Skeleton, Minotaur Skeleton, and probably a spellcasting variant.
They mentioned there would be new weaker Liches like... apprentice Liches? Maybe those two on the sides are? Boggles the mind how that works... if you can become immortal even as a low level wizard, the world would be full of Liches...
This was shown months ago, but here it is again, Kuo-Toa Archpriest.
Quaggoth.
Probably the Androsphinx? Can't say I am a fan of them being just winged Lions now.
More animals, including Mammoth and Saber-Toothed Tiger.
Some likely new plant creatures, including topiary animals and a weird tree.
Shrieker and Purple Fungus.
Behold.... erm, Gas Spore.
Going out on a limb here, and guessing this is the Dao. The whole earth powers and crystals growing out of her shoulders thing.
Unleash the Kraken! And yes, they are now back to being giant Squids instead of the Clash of the Titans inspired look.
Giant Wasps
Rodents of Unusual Size
Griffons, arctic variety. And some very foolhardy egg thieving Kobolds!
I am unsure if this is the Galeb Duhr, or an Earth Elemental.
Sea animals - Orca, Shark, Giant Crab, Giant Eel. Plus a Sea Elf (or Malenti...)
Are you ready to Roc?
This is probably some higher level Earth Elemental.
Bearded Devil/Barbazu. Guess they dyed their beards purple now from the 5E green.
Barbed Devil (Hamatula)
Rakshasas! I am really happy that WotC revived the original lore, where they can now have other animal heads - like Egyptian Vulture, Goat and Crocodile.
This was posted, but was not mentioned what it is - pretty sure this is the Bar-Lgura. It seems having misshapen forms, multiple eyes and mouths and mutations is going to be a thing for Demons in this book. Goes well with all the chaos they embody, I guess!