Yeah, this is the one I was going to mention. Somebody posted a pretty damn neat summary of how they created a custom 13th Age setting, complete with icons, based on a session of Microscope. Gave me a lot of inspiration for coming up with a set of my own, actually.
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As for me, I think creating a world is something that needs to involve three elements.
One: the DM needs some core idea of what the world is, or how it works. I don't mean in the sense of writing a specific setting bible or whatever. I mean in a narrative sense. Is this a world that rewards chivalry and showing mercy to your enemies, or a world where only the brutal and cunning survive? Is this a world where the average person rarely sees anything fantastical, but the PCs are far from average? Is it a world where stuff WE would consider fantastical is popping out of the woodwork? Or perhaps does it have a mixture of both--cities and towns where life is normal and mundane, run through with veins and deposits of the magical and stunning (and terrifying)? Answering questions like this can take time and development--and may be something you want to decide during or even after basic chargen stuff is over. I tend to play LG Paladins, for example, so many of my DMs have made Paladin-y behaviors
potentially rewarding--rather than forcing me to slog through a world that is thoroughly
and rightfully antagonistic to my character's ethos. But a group heavy on Rogues and underhanded personalities may find that kind of world a slog instead!
Two: the DM and players need to throw in mixtures of their own contributions to the world. A Rogue rarely exists in a vacuum; there is a context of crime and fences and intrigue, or perhaps brutally oppressive regimes and the struggle to survive, that gives birth to the Rogue. A Paladin often has a knightly order, or a title or position in a noble's court, or perhaps (like a Cleric) a position within a church. A Warlord connotes the existence of organized military or paramilitary forces. A Bard learned music, stories, and poetry from somewhere; likewise a Wizard had to have a school. A back-and-forth negotiation of the details of these backgrounds goes a long way to fleshing out the world, and to giving the DM solid, interesting plot hooks to exploit both in the short and long terms.
Three: the DM needs to respond to the choices and dynamics of the player group. If the Paladin becomes disillusioned with her faith, that opens an opportunity--whether to restore it or change it. If the Fighter goes from scorning the power of magic to being enamored with it, that's a golden opportunity to showcase the power and danger of magical abilities. The Monk has decided that the Rogue has great potential for recruitment (Rogues want high Dex, for stealing, and Wis, for trapfinding, after all...) while the Rogue has decided that the Monk needs to learn what she's been missing while cloistered behind monastery walls. Etc. Turning the examination and presentation of personality facets, as well as the relationships between specific NPCs, into plot hooks and encounters is a GREAT way to explore the world, establishing new things within it while anchoring them to stuff you've already made 'real' in steps 1 and 2.
And notice that most of this happens
during or after play has begun. This is why it's so important to do things like have a pre-campaign-start character creation session. Details like this, or at least the groundwork for them, can be laid at such a time, and help make the players feel
familiar with the world even while they are still
surprised by it.
