Here's a Wings of Fire Minecraft resource pack with multiple elytra textures and a few other fun things.
This pack only works in Minecraft Java 1.13
You must have optifine.
Make sure to have Custom Entity Models and Custom Items on.
Options > Video Settings > Quality > Custom Entity Models/Custom Items
All you have to do is rename the item to the correct name (below) and it will change it's texture.
(It is case sensitive, so you have to include capitals.)
Bow = Blowgun
Stick = Invisibility
Stone Sword = Claws
Iron Sword = SerratedClaws
Lingering Potions = FrostBreath
Diamond = Sapphire, Ruby, RoseQuartz, Opal, Jade, Onyx, Amethyst, Topaz, Garnet, Citrine
Iron_Ingot = Copper, Silver
Leather Chestplate = Satchel