I was extremely bored, so I decided to add the custom rocks and pits from Fiend Folio to Antibirth.
Also ports Repentance floor props to the game.

I couldn't edit the pits and rocks that the regular unmodded rooms used, which means that Basement and Cellar do not have custom pits, the Necropolis reuses the same rocks as the Depths, Utero reuses the same rocks and pits as the Womb, an the Chest and Dark Room do not have custom rocks or pits, but I could edit what rocks and pits the modded rooms from Antibirth used.

Also backports Repentance floor props to the game.

Antibirth files are pretty interesting to look at.

Credits:
P.E.N.I.S (now apart of Nicalis I guess): Made Antibirth
Rick: Made Rebirth unpacking tools
Team Folio: Made Fiend Folio
Edmund McMillen and Nicalis: Made The Binding of Isaac: Rebirth

Mirror link for people who don't wanna sign in: https://www.mediafire.com/file/ihemh2bjabt37yo/%2521fiend_folio_rocks.zip/file

Also check out Repackance for Rebirth!