Each animation is an ordered list of images (textures) that are stored in Mojang's database. Because Mojang never deletes skins on their database, it's easy to make an animation.

To get started, you'll need to take the basic texture:
http://textures.minecraft.net/texture/d6a4b88a297c78f9dd53ee8c7164dda0ded7e988382555bc7d89c901922b32e

This is a normal emote head. Duplicate the file and make changes to make frame-by-frame animations.
After finishing, send a folder with all of the textures in the UC Discord and someone will add them to UltraCosmetics!

Let's say we have 5 images: image 1, 2, 3, 4, and 5.
The animation will be played as:
1 -> 2 -> 3 -> 4 -> 5 -> 4 -> 3 -> 2 -> 1
Each frame/image lasts for 1 second (20 ticks), and the animation will repeat after completion.

Questions? Open an issue or join the UltraCosmetics Support Discord Server.