I can see where you had trouble with the contrast, you probably wanted it to be dark with some bright highlights, but you couldn't get your color ramps where you wanted them without reworking the whole thing and adding too many colors. I loaded it in grafx2 and messed with the palette and I can see how the detail in the face is ruined when you brighten the lightest of your four browns...
More contrast, or atleast make it lighter! Would be awesome if someone carved this outta a stump :3
i love how you got it clear that it was made of wood and got it to closely resemble a tree while making it obvous its a skeleton. The only thing that could use some work is the back part of the hills, they look a bit plain
Spectacular! The background is lacking though. I think the others were right about the contrast