it has since come to my attention that this is literally just free cosmetics on the cardfaces, but fuck it, it suggests content in the pipeline and poncle of Vampire Survivors loves crossover updates/dlc so this surely means good things for at least one of my two favourite games
Do note if you have changed your card art before this update, you will need to re-copy+paste the card art since the update applies the original art. The update only changes the face cards, so you can have custom artwork in addition to this update.