readability is a huge problem here. everything is vying against everything else for attention. sometimes less is more, in this case everything is too textured, too noisy. it's all on the same plane.

there are some great tree threads over at pixelation. basically, you need to know the anatomy of the tree. don't worry about the individual leaves at all (until the very end). worry about the large clumps/clusters of leaves and what they say about the branches underneath.

Thanks! I have uploaded the whole screne with the trees, aswell as another tree.

There's almost no vlume on the leaves. You just copied and pasted the same leaves all over the place. The branches suddenly stop somewhere in the leaves ant the texture on the tree trunk doesn't look like bark. You could add a ground at least. You should either add a background or transparency. I recommend an actual backgorund for this one though.