The Crystal Gems Expansion Universe is a fan concept by Mr. Napcakes that, in the future, the Crystal Gems expanded to protect life on other planets as well as Earth. Using a rogue, already dead planet as a Kindergarten, the Crystal Gems created other gems to spread across the universe in order to protect other lively planets.
Gems made at the Kindergarten aren't segregated into separate groups, but rather randomly made. They have no set objectives and body types.
Humans traveled as well. In this fanmade concept/universe, the gems actually interact more with the humans in the future, and eventually set off to space together. Each planet protected by a branch of gems has at least 25,000 humans.
Anyone can use this universe. Whether it be fanon or just somewhere to put your characters, everyone's free to contribute.
The Planet Fortissimo Branch (Created by Mr. Napcakes)