And, to top it off, some game design ideas from Fish:

• A ta'nari who had been caught by his enemies and turned into a human. Now you want out and you want revenge. It doesn't matter in which order. All you have to do is survive, because you were one damn good ta'nari, which means you have a lot of enemies.
• A human taken from the planes and brought to Sigil, bearing the personal mark of the Lady of Pain, Peace be upon her. The Lady of Pain wants you to do something, you don't know what, and someone is very intent on stopping you. You bear her mark which has to have some kind of power to give you whatever you want... alright, an editor-program right in your inventory.
• You play as a killing machine construct, created by a sorcerer of great power. He gives you missions, you go kill stuff. Until, that is, you are subjugated by a higher power and sends you on a quest that involves what you do best, killing, and so much more, like cute little girls who need to find their lost parents. Saving cats up trees in the middle of the Gray Waste. Oh well, it's a living.
• You were always an outcast, always in the shadows, always a watcher from the outside. The life of a wandering minstrel suited you. Then you heard of this hand, around which an entire secret society has built up around. It has strange and miraculous powers, which is fine, except you keep hearing voices that tell you to seek out the hand. Armed with your extensive talents as a performer, an enchanted instrument that bends the minds of the listeners, and a dark secret that you keep hidden even from yourself, you follow the voices across the planes. Every life has to have a purpose, or else everyone would simply stop.
• You are permanently cursed to pay for one hundred years of suffering that you caused you must pay penance for ten thousand years or else. Or you could just skim off a couple thousand years if you take out some really bad men. Or you could find someone somewhere to free you of the curse, reclaim your lost youth, and then take some serious vengeance on those who cursed you.
• Once you were a proud and noble god, until you got this great idea of liberating Sigil from the Lady of Pain. Now you're no longer a god, you hurt like hell, and there is just this smell everywhere. Your followers have abandoned you for dead, and you can't even pray to a higher power because you are a higher power. To make things worse you have this pesky thing called mortality. From what you've heard, death sucks. From what you can tell, so does the food.

  So those are my ideas. I figure they would, at least, make interesting NPCs.