Do you have shots of the trees ingame?
At the given screenshots they are way too flat, they are missing depth and volume.
IMO, you have to integrate shadows of the leaves somehow, you can take photographs or duplicate given paintings of leaves, and change the shape of the duplicated a bit, make it darker and put it in the back of the other leaves.
I would bake the shadows into the branches as well.
In blender you can bake the shadow into a texture with a second uv, you know that, and you can bake the tiled texture into that second uv/texture as well, save both textures in different tgas and combine them in Gimp.