Snover is very cute. These little evergreen-like creatures are known to be friendly and inquisitive towards humans, and will even gather around human footprints like we do with yetis. Aw!
Visually, I do like their design a lot as well. The brown, dark green, and white palette is unique and looks really nice, and it's not overly busy. The brown bottom kind resembles a pine cone or maybe bark, which fits with it being a "young" tree. I like the tail as an extra beastly addition, and the head fur resembling a snowy mountain peak is also a nice touch. Good stuff all around.
What's neat is that instead of just becoming a bigger tree creature, Snover evolves into the abominable snowman (that also happens to be a tree). It works great conceptually and gives the line a unique theme.
And visually, I like how it strategically drops the brown from its palette in favor of emphasizing the white and green. Said colors are nicely balanced, with it having a primarily white body with just a few accenting points of green. The shaggy face and big ol' eyebrows are also good and give it a great expression.
And mega Abomasnow's pretty decent. I really like how it's moved into a semi-quadrupedal stance kind of like a gorilla—it makes it look all the more dangerous. I also like that it doesn't really add any unnecessary new elements, instead just changing the anatomy up a bit, adding more fur, and expanding the four spikes on its back into a set of icy cannon-like structures.
My only issue with it is that the sheer amount of fur is a little overwhelming—there are at least five rows of it from the head back, not counting what's on the back spikes, chest, and arms. Obviously you want more fur than the original, but I feel like just dropping one or two of the back rows and simplifying the ones around the back spikes to one might've made it just a little easier to read. Still, not a big deal in the long run.
Overall, some really excellent weird tree creatures.