Heheh
I think trees needed more leaves and branches (added no big branches since I wanted to stay true to the original tree) (: I also played around with the trunk and did this and that, and I hope you can learn something from it.
I thought that the trunk was somewhat of a mess, so I desaturated it and, eh, redid it and chose completely different colours. The problem is that I worked against a black BG, so it all might be a bit dark
>
Anyways, when you make the leafage, don't try to make it some kind of cloud-shaped tree:y shape, just quickly scribble where you think leaves should be and then blot around with a 2x2 brush or something like that, just blot out leaves and leaves and leaves and leaves real rougly. After that, when you polish and clean up, the tree-feeling should already be there, so it's just up to you to refine it. (:
It's one way of rendering them, at least O: