Already found 1 thread about that here... but with no answers so I am going to suggest it again.
Simply Heraldic Horsearmors.
I got 2 ideas about that.
1. You can implement the Armors, or maybe just some horseclothing if you don't want to leave speed/maneuver.
If that isn't working there would be:
2. Add between 1 or 3 new horses with heraldic armors, or more... usually there should be of each horse a heraldic version.