I myself am going for a theme of travel with a focus on wandering and impermanence/passage (of time, of sights...)
Really don't want to play a gatekeeper of worlds, so I have been thinking about the topic of spheres. Cyclone even talked about the possibility of tuning oneself to the sphere of Galbar itself, which was a thought that has been on my table, but depending on what other ideas people throw around and what areas lack a god, I have a few ideas of my own concerning seasons (the big one for me), or the moon, or the stars, or wilderness, or even death.