I had a specific DC fandom line idea/request that I've been itching to play. A century ago a group of crime families in Gotham invoked magic to maintain their hold over the city. Only in so doing, they ended up creating a curse on the city that has recently been awoken. A mystical darkness is stalking the underworld and creating havoc. The descendants of those families/crime bosses in power now are paying the price. How they deal with it we can plot out and play. This line could involve canon characters such as Batman's rogues' gallery, the Batfam, and the magic crew (Zee, anyone? Corrigan?), or OC's. Whether the criminals band together, seek out the help of heroes, clash or bond is entirely up for discussion. I just love the idea of playing around with past and present actions colliding, and creating a new danger within the fun established city of Gotham.
I'm only looking for PSLs, but I entirely welcome playing multiple characters in a line and creating something plotty that leaves room for plenty of character development. Additional fandom PSL ideas can be found this way.