Most games (D&D XEd, White Wolf's Storyteller games, GURPS, etc) all have the concept of arriving at a scene or having a scene occur. I am suggesting mapping a location for a key scene to some other story (or maybe as the whole of a story). As examples...

The House for Bad Murder TM (as in How to Host a Murder, Classic Murder-Mystery Films/Plays)
A marketplace or slum district (think of any applicable chase scene)
Meeting with Mr B. Bad-Evilguy (either the EPIC CLASH or the Obligatory Preamble Skirmish)
Scene of Nasty Magical Mojo (place where Demons were summoned, sacrifices of many children, etc)
Pious House of Good-Cleric Steve

I'm sure you get the idea. It would come with some text (either on the map or just in the thread...)
Open-ended... yes.
Potentially Heaps Of Fun? Yes