I really do quite like this picture, though as you say there is something a little off about it.
As far as i can tell, it simply comes down to defining the shadows, and separating the fore and backgrounds.
One of the most distracting things in this image is the barely noticeable difference between the leaves and the dress. I would suggest introducing a few darker reds and browns amongst the leaves, and possibly a few dark yellows. That should make the foreground pop a bit more.
As for the foreground, I think just adding a bit more depth of colour to the shadows would do the trick. Orange is one of the hardest colours to do shading for, as we automatically tend to try and shade with reds. I would try shading with some brown and then add a bit of colour to that.
I hope that helps you. But as I said, It is still a lovely artwork ^_^