I've been mulling it over for a while, promising my son, and now some others, that I'd be ready to run a new campaign world soon...
Lot of ideas floating around in my head. Here's a detail free list of some of them...
Citta (The World City) and The Outside Inn
Tesseracts, Klein bottles, and Mobius Strips
Portals, Gates, Windows and Doorways
Space Travel, Time Travel, Mutants and Aliens
Primordial Gods, Forgotten Gods, Missing Gods, New Gods and Dead Gods
Golden Ages, Apocalypses and Post-Apocalyptic Ages
Cursed Lands, Blessed Realms, Parallel Worlds and Skew
Memory, Masks, Dreams and Nightmares
Eternity, Stagnation and Change
Birth, Life, Sleep, Disease, Madness, Death and Rebirth
Swords and Sorcery
Ann Rice, M.A.R. Barker, Gary Gygax, Isaac Asimov, Robert Heinlein, Frank Herbert, Arthur C. Clarke, to name a few...