Hey All!

I am a newbie on the site and have been looking for some forums to help me get some creative juices flowing.
I am a newbie GM - having only GM'd previously for a short stint of our Pathfinder Campaign (Jade Regent).

However, we are starting to think about our next campaign and the GM has graciously handed me the torch to take over. We have decided to build a new Campaign based off of the TV show Supernatural.

I have already built the classes and have a base story. We are using Dungeon World as the base rule system and style for the game, as we want something more story based then what we are playing now. Less math, more epic story!
I've got the Campaign Front almost fully built, but am leaving some room for growth there. So now I am moving on to building story fronts or sessions.

I would love to get some thoughts on cool fronts and idea's I could use for these adventure fronts. I'm looking for idea's for vengeful spirits, witches, ghosts, shapeshifters, whatever you've got! And I would love any help in regards to how many fronts I should be building for my campaign. I'm guessing something like 40-50? Again, I want to leave room for growth as needed, but how do you decide how many sessions you need or fronts for the entirety of your campaign? Is there a good rule of thumb?

THANKS!