Not seeing any real problems with this piece, but it would help if you told us what its intended purpose would be -- i.e. background, middleground, tile layer, etc., and showed some hint of what characters/scenery would go with it maybe. Otherwise, there's not much to say since we don't know what your purpose was. Both color and construction-wise, it looks great imo, but that opinion could change depending on its context and its intended use.
Show me where the player would be standing in this image and what he looks like, for example, and I can give you more critique. If a tile layer is supposed to be overlaid on top of this, assuming this is a background image, show that too.