I made a custom door plugin for my server, and Psycheer recommended that I make a feature request for this to be added to ItemsAdder.
Oxidized copper doors and trapdoors with blank textures are used for the hinge detection and hitbox.
Item displays are used for the custom door texture.
My plugin only allows for 2x3 custom doors, but this same method could be used for doors of any size.
More info can be found on the GitHub repo: https://github.com/GamerGuyD3/DoorMaster
Feel free to use any of my crappy code.
Showcase of custom doors
Demonstration of door hitbox
