CircleDrain;
First of all, good job on taking on such a challenge!
However, you got some major issues with your sprite.
Don't worry though, that's why we're here: to help each other and improve... anyway let's get started.
Your tree's leaves are scattered all over the place (maybe I am overexaggerating a bit :P) and aren't arranged in a way that makes sense, it looks like there are some leaves scattered on a floor...
The trunk needs some work too, especially the shape.
On another note the whole thing looks flat: you need more contrast to give your tree a good shape and you need more contrast so it won't look flat.
I have found a great thread with progress shots on spriting a tree, I heavily recommend you to give it a look ;o
http://www.wayofthepixel.net/pixelation ... ic=10520.0
Anyway, I've got something for you guys too, started workin on this little guy, its still a bit "raw" but i like where this is going: