Nice generator. The following suggestions are provided.
1. Add a hint to spawn: The number of frames it takes for the planet to make one revolution. Games often require continuously rotating planets, but the number of frames generated is often not enough to make the planet rotate perfectly 360 degrees, and the user of this generator has no way of knowing how many frames it will take.
2. "star" planets generate with a lot of white space around them, which is different from other planets, maybe this is a bug.