Good job, but could still use polishing improvement:
- blueish hue shift on the trunks is a good way to make things look distant, but you _must_ accompany this with desaturation. If it is just turning to eletric blue, it doesn't work.
- outlines must really be that : _out_lines. When the trunk's line keep straight vertical where the branch grafts, you break the illusion that they're part of a single thing and present them as two different objects put aside of each other. Look closely at Gill's edit : he's englobing the whole tree in a single outline, which reinforce unity of the volume.
Welcome to Mr. Mushroom, too. He points out your remaining major weaknesses, though:
- jaggies in the organic outlines (that is, it looks like your curve is changing direction quite often rather than being smooth).
- facial features that are small, close to outlines and thus hardly readable. I guess you want to give him fangs, but they don't look like some.
HTH. I'll try to propose an edit on Mr. Mushroom within a few days.