*OPTIFINE IS REQUIRED*
In order to obtain these variants, you can rename an Elytra in an anvil to have the keywords:
Squirrel
Alien
Moon
Zombie
Peafowl
Kris
Secret_agent
Blacksmith
Rain_shaman
None of the keywords are case-sensitive, and you can even add more words. Example: Names like "Wings of Peafowl" or "zombie cape" will still work as long as you use the corresponding keyword.
(You can view each texture and their corresponding keywords in the Images)
Note: You can even use this with my other packs, "CouncilRyS Capes", "HoloMyth Capes", and "HoloAdvent Capes" to have all of my Hololive themed Elytras!