Regarding history, one of the things I've rarely seen in a module and don't remember ever seeing in a setting is variation or perspective. For example, one of the complaints I've seen on the boards is that too many players know the Realms better than their GM's ever will. There's simply too much published material available, and too much of it is "canon". Consider instead:
600 years ago there was a great war involving almost all the races. Each race teaches a slightly (or not-so-slightly) different version.
*To the dwarves, it is the War of Vengeance (the elven empire treacherously attacked them).
*To the elves, the Rebellion (the primitive and immature humans rebelled against their rightful rulers - elves).
*To the humans, the Days of Freedom (the downtrodden humans asserted their rights to equality among all the races).
*To the hobgoblins, the Betrayal (they were betrayed by their allies, the orcs).
*To the dragons, the Bloodletting (the toll was so great, whole regions were depopulated).
And so on. Each tale will have some truth and some fiction. By building such uncertainty into the world's history, it adds verisimilitude while also permitting me, as GM, to decide which pieces are more accurate - making my world a bit unique compared to everyone else running the same setting.
As a GM, I add my own tweaks to any setting I run. I'd just like to see a setting where the history facilitates this.