I really likte it, it's great that you show that you can model different seasons for the same scene. I have some suggestions for improvements. It's great that you have used different hues for the grass and trees, but I think that you could add more flowers to the trees just to make a bigger constrast between them. Atm you can really see the differences between what's winter and fall, but the spring and summer dosen't differ as much. What you also could do is to add some pool of water to the autum scene, as it does rain alot during that season (at least here in scandinavia ) This is just suggestions. I think you have done a great job, keep up the good work!