I am not very familiar with WotBS. I have more than enough APs for awhile. That said I think I would like a shorter AP, maybe 1-10 or 1-15.
Start in a city. We have done the quaint villages to death. The first adventure can be an mystery; just don't forget the three clues rule.
Another thought, could you do a tight module trilogy with the same mystery, but then expand it out more (like layers of an onion)?
Decent names. Fantasy worlds are full of
kenning words (Sandpoint, Freeport, Waterdeep). Maybe something different?
I like demons, devils, and outer planar creatures, however, they have been done to death.
Pirates are cool, as are Cthulhu elements, something more specific like the Yellow Sign. Like a more cool version of Freeport trilogy.
Vampires are cool, too, especially if you can put a unique twist on them. Lyncathropes are cool also.
Here are some weird ideas I gleaned from the thread**:
* An "ancient good", a "new evil"
* Planar Pirates. Could we have planar ninjas, too?
* Reoccurring "good-guy"
** only try these if you can pull it off