I am not a *ahem* artistically gifted person, nor do I have the experience of a lot of people here, but I will give you my criticism based as the end user. The water looks very nice, and I really like it. However couple of things that I don't like: the hills don't have nearly the detail of the water and look out of placed with it, also the water doesn't have a very good edge with the hills...it just hits the sides of them. In real life at the edge of water there is always some border: sand, vegetation, mud, rocks, cliff face, etc. Maybe if you put some vegetation on the hills and got it denser near the water edge and had it sort of over lap the water. or make the hills rocky like the ones in the Scottish Highlands.
And I think a windowblind with that color scheme would look nice, but the colors have been used in a lot of other skins...probably because they, look nice together.