The world generator only creates a single planet that can be edited in many ways. Making it a universe generator would add things like multiple moons and suns, constellations, and other planets solar system. I think this will be very important for things like engravings and statues, since the sun, moon, etc. had a strong influence on ancient spirituality.
A solar system would have to include at least one star and one planet.
The sun star could be a class O (extremely large, white, least likely to occur), B (very large, blue-white, very unlikely to occur), A (large, unlikely to occur, blue), F (likely to occur, yellow, average size) G, (Most likely to occur, average size, yellow), K (likely to occur, orange, smaller than average), and M (unlikely to occur, red, very small). The effects of the type of sun-star could be the temperature of the planet.
Possible moons depend on how large the home planet is, (larger world = more moons), moons would effect ocean currents of the planet, although I’m not sure how this would be incorporated into the game.
Stars would only be recognized by civilizations in the form of constellations. (ex. On the oaken chest is a masterfully crafted image of swordsmashed the constellation in cowhide leather.)
Other phenomenon like black holes and supernovas would likely be too overly complex just to destroy the entire planet.
This is all I can come up now, but I hope it will be considered to be put in the game