Resources
Non-Cauldron content we created
SotM custom promos: Promos for official SotM heroes.
Joke decks: Several fun, less-balanced decks with varying amounts of seriousness.
Cauldron resources
Text-based card spoilers: A Google spreadsheet with the card text for all decks.
Misc Cauldron Images: Includes different formats for divider images, nemesis icons, character card front & back images without any text, environment card back images without any text, hero titles, nemesis icons, etc.
Unofficial resources
Links to Cauldron-related goodies that I don't maintain or test, but which other people from the BGG community have helpfully put together.
Vertical Dividers: Vertical Cauldron (and other) divider images created by BGG user HikariStarshine.
Oversized Villain Cards: Oversized Cauldron villain card images adapted by BGG user Meat.
Yoshi's Scum and Villainy: Thread with adaptations of the base Cauldron villains to the Vengeance format, along with other conversions and customs by BGG user the_yoshi. (Note: I haven't really played Vengeance format much and I can't comment on their balance.)
Randomizer & Game Aid: Browser-based/downloadable game randomizer and setup tracker by BGG user catwhowalksbyhimself, which includes all the official decks as well as some of the Cauldron decks.
PBF Spreadsheet: Reference spreadsheet primarily for Play-By-Forum games by BGG user jsdougan, with transcribed text of all the official decks as well as the Cauldron and Cauldron: Experimental.
PDFs for home printing: PDFs for a bunch of decks that are formatted for easier DIY printing and assembling, courtesy of BGG user dobrazil.