when you get on the horse and get to like you and then when you open the horses menu and you put on the diamond armor and then put on the saddle the back round show the sky or show whats behind you, but it upside down.

1.Get the horse to like you where it wont kick you off of the horse.
2.Get on the horse.
3.open the horses menu.
4.Put on Diamond horses armor before the saddle.
5.Then put on the saddle last.