Twin Planets

Well, got my second lesson with photoshop at school today, and with the things I learned I created this :3 Most things worked out, exept for the planet in the top left of the picture. I used the moon for the icy-jungle planet and Mars for the- well I don't even know what that one is. Top right has to be a sun, but that could be better.
The drones/ships you see in the picture are actually parts of a motor.
I think it looks good as it is, but I am still learning, so please tell me what you think of it