The planet and large moon/secondary planet are a bit too full of flat color for my likes--the enemy ships and player have more details and so using a small amount of dither like you did on the planets looks fine on the ships. But on the planets it just looks unfinished. Also, if the planets have no craters there should be a reason. Earth has life and an atmosphere that leads to very few craters, but the moon, even though it has a smaller surface to be hit by celestial projectiles, lacks an atmosphere and has many craters.