Minecraft 16w38a, Minecraft 16w39a, Minecraft 16w39b
Linux, Java 1.7_111
If an armorstand is first to render, elytra will render on it with additive blending, so will every armorstand and one entity rendered subsequently, if there's no items in the world.
Elytra on players will render with broken textures if they're holding an item and with their skin data if they're not enchanted.
Note: this is a complex issue and I'm not sure about whether all the details are correct.
The elytra texture is messed up when one of the hands are full it shows the textures of all the items in the shape of the elytra and with both hands empty it shows your skin in elytra shape