The colors give this a nice feel to it. I wouldn't worry too much about details on the leaves because the position of your light source means that the leaves should be mostly in deep shadow. It's mostly the edges of the leaves that'll be seen. On that note, I would recommend having more shadow on the tree truck because the light doesn't seem like it should be able to wrap around to the side of the tree facing the viewer.

One thing that confused me at first was that the ground seems lit as if it was water, but it's green, so it must be grass. Try taking the two lightest shades of green and making them a bit darker. The sudden jump in lightness from the third lightest green for grass to those two under the sun looks kind of like the sun has a reflection in water.