Flat worlds, toroidal planets, cube planets, etc.
My longest-lasting conworld existed on the inner surface of a sphere with a light source at the center. I briefly considered having Yih (the homeworld of the yinrih) be a toroidal planet, but thought it was too out there and decided to give it a ring instead.
[off topic]
If you haven’t heard of him, look up Golden Age science fiction writer Poul Anderson.
He’d start with a star, figure out what the planets would look like, and then populate the worlds.
https://en.wikipedia.org/wiki/Poul_Anderson