You chose a poor sky. The ship is completely out of place. There's no fog or decent lighting. You used far too many waterfall doodads to cover such a small area. You have floating rocks and waterfalls (at the top some waterfalls are higher than others). The cliffs are very plain and boring.
If it seems like I'm trying to tear you to bits.... I'm not, you have a good starting point here. But you need more practice....