I'm reworking the way modding works, and because of that custom sprites don't work in this version. They should work again after the next update.
For now you can download the older version of the game using the itch.io app: https://itch.io/app
("Library" -> Click on the game -> Click on the options gear icon -> "Manage" (or "Install" first if you haven't already, then "Manage") -> "Switch to another version")