This is pretty damn charming. Nice work on the face.
The pose is isn't very natural - maybe just abandon the stepping-up part altogether & have him lean his weight on the tree. Alternatively, abandon the tree-grasping & have him climbing the hill mid-stride.
I don't mind the engorged forearm thing (in fact I quite like it) but the anatomy needs work, & would benefit from less definition there in particular, because it's less clear there whether the highlights are light or whether they're just delineating particular muscles.
Navel is way too low (Unless it's a urethra sort-of thing). Knees look a bit concave.
more vibrant palette choice
Those edits are the most fun.
After drawing some rocks recently, I've been able to get a rocky appearance with gray midtones & warm shadows. I don't know why.
I might have boosted the contrast too much, I can't tell after a while.