Depending on what type of gear you wear, it alters the Elytra's texture.

What I expected to happen was...:
to wear a regular Elytra.

What actually happened was...:
the Elytra's texture took priority of whatever single piece of armor you wear and/or if you held an item in either hand.

Steps to Reproduce:
1. Put the Elytra on.
2. Switch to third person.
3. Toggle what you wear on your head and whether or not to equip any item to either hand.
4. Repeat step 3. but with the boots and then leggings.