A free mod for Mount & Blade II: Bannerlord, by Eykonal.
Eykonal’s Banners is a simple, yet useful mod that adds custom banner icons for your profile. It doesn’t have any code in it and won’t affect gameplay, but it is still useful to have it on your profile.
You can choose a number of icons from the list that are included in the mod and you can add as many as you want. The icons are easy to use and have been designed to fit in with the rest of the game.
You can find the icon for the byzantine empire in the main menu and for the other historical eras in the game.