
As we develop character sheets for NPCs, I wanted to hear what people's thoughts were regarding levels for NPCs. A campaign world with NPCs who are upper teens has a very different feel than one with around 10.
My personal taste is that we would have a handful of characters in the entire setting that are in the upper teens. These would likely be the most powerful NPCs in the world. Then we would have most leader-type NPCs of medium to large organizations with level ranges in the 11 to 14 range. Finally there would be leaders of minor organizations in the 8 to 10 range. Anything below that is more "average" when it comes to NPCs of note. The final thing to remember is that anyone with divine spells is going to likely be 10 or below since divine magic did not exist prior to the Collapse.
Does this sound like a reasonable set of guidelines? Do people think notable NPCs should be lower? Higher? Other suggestions?

Levels
I like higher level NPCs only because it means I can manipulate and tweak them to make them truly unique whereas at lower levels you have access to less customization. A higher NPC also limits the number of lower level PCs trying to attack them under the normal context of the module. You know guys like Gandalf or Elminster can be in your module without any worry that a crazy PC goofing off will try and attack them becasue they will most likely be vaporized into pink spray and goop. I do like the idea that there should be maybe only at most 10 or 15 of these "supers" running around so that it makes them even more notable and cool when they have cameos.
With Divine magic being a new thing would there be an organization or people that actually sees them as Infernal? Maybe one created to hunt them down and their false gods? Maybe like an exagerated battle between the scientists and religion except between the mages and the clergy. "We know what causes these so called miracles it is man and his manipualation of Mana not some unknown god from outerspace!" Just thinking out loud.
It's also possible for the NPCs to have no levels technically since you can really have them do whatever you want throughout the course of the module even if it normally wouldn't be allowed because of a level restriction. Sometimes it's more fun to make the PCs not really know how baddass the badguy really is untill they figure it out. I remember a game I played where we essentially made our fantasy D&D counterparts (who hasn't?) and the DM did the same thing for the main villain who we really had no idea what his class was. We'd meet him at different times and he would almost mimic different classes. He was weilding magic at one point, wore spiked leather armor, and was awesome in melee combat with two weapons. Turns out he was a bard when he started singing a battle hymn while he was fighting.
I like lower levels
One of the things I liked about Eberron is that by the time you're level 10 or so, you are Big Damn Heroes capable of truly amazing feats. I much prefer that to Forgotten Realms, where you have to hire the neighbor kid to shovel the Wands of Wonder out of our driveway every morning, and 30th level NPCs own every third tavern.
Seriously, though, I think people like the heads of the Arcane Schools should stand out because they are 17th level, or thereabouts, and can actually use things like 9th level spells.
I also like divine casters being, in most cases, even lower than 10. A 5th level divine caster is going to have people crowding around them asking for supernatural cures for disease and that kind of thing in my view.
I see 10th level as the chosen divine prophet of deity X, the equivalent of the head of the arcane school. I like the idea that for powerful divine spells, the PCs will have to have a divine caster among them, or find a way to contact an Outsider to help them.