I proposed an idea for the Dark Sun setting last year. That is, a supplement for Dark Sun similar to the Legends of the Twins supplement for Dragonlance.
Proposed Format (Work in Progress)
The Occulted History of Athas. Alternative histories to unearth. Maybe Athas is the homeworld of the gith Forerunners. Maybe the gods were killed by the sorcerer monarchs and the Dragon in an act of utter blasphemy. Many possibilities. The Free City Can Be Any City. A rebellion could take place in another city instead of Tyr, with that city becoming the Free City instead. Rumored City States. Are there other cities around Athas? The are rumors about them. Lets see what the rumors have to say. Different Defiling. What if defiling isn’t what destroyed Athas and Athas was originally an impoverished world. Perhaps defiling drains the happy emotions of sentient beings. Magic drains happiness of people, making them hostile. Or defiling might to something else altogether. War Between The City States. Do the city states have any rules of war? How come all the city states aren’t destroyed?