Watching the video, the spikey thing under the abashai in the illustration at the top of the thread is a Sorrowsworn - the Lonely. The deformed thing below the eladrin is a rutterkin (one of the few classic demons that had yet to be updated to 5e - so I'm quite happy to see they got in as they are on my personal list of creatures I was wanting to see updated).
Also shown in the video, but not among the illustrations at that top of the thread, are:
Sea Elves (at 23:20).
Sorrowsworn - The Wretched (at 32:30)
Unnamed red ooze creature (at 54:23) that they said they are just previewing and will actually go more in-depth on later.
There is also several more pieces of art work we've already seen, like Moloch, the Astral Dreadnought, and a few others...