Many years ago, Dr Zhark created the Mo' Creatures mod which included horses and horse armor (before there were horses officially in Minecraft) and a few other animals. I fell in love with the mod and used it exclusively because of this.

So when Mojang introduced horses officially into the game, I pulled those horse armor textures from the mod for personal use (with some adjustments), since I thought they looked really great.

And when Mojang changed the horse model, I modified the original Dr Zhark textures to fit the new blockier horse model. I'm sharing those modified Gold, Iron, and Diamond horse armor textures with everyone in this resource pack.

Enjoy!

Dr Zhark made the mod open source: https://github.com/DrZhark/mocreaturesdev

Edit: The new Crystal Armor texture is an alternate to the current Diamond Armor texture; its texture is located within the actual horse armor folder with all the other textures. Just remove the "alternate" from the name to replace the current diamond armor texture and to use the crystal armor texture.