This is really nice work, reading the other reviews I fell that you are being beaten into a pulp, I trully thing youve done a wonderful job here, you have chosen pale mystical colours that help blend the whole picture into one piece. The way the tail wraps around the moon is great too, it has a Rodney matthews look about it.
The only pointer is that the back right foot of the horse looks as though it should have angled towards the floor a bit more. it just looks as though your horse is running on a flat surface, yet it is on a hill. one tweak and it would be a spot on wall piece.