The Banner of the Kage was a Templar Tradition from back at the orders original inception. It was the brain child of Tera Byssta much like the Templars of Twilight Insignia. She believed, and it was accepted that, being Kage was a symbol of importance to the individual, and to the Templars as a whole. Each Kage was different, and as such each age of the Templars was different during the reign of that Templar. So at her suggestion, and the agreement of the council, every Kage upon being selected had a banner designed for him, that would be unique.
Each banner represented the individual as a person, or a Templar, or both. It bore their family seal, or something relative to them, such as a special title, or something associated with race or spirituality. No two banners were identical, even those that appear to be the same have subtle differences, changed colours, altered fabric patterns.
While a Kage reigned over the council, The banner, which was normally a meter wide and 6 long, resided behind the Kage's chair in the council. When the Kage retired, or was dismissed, his banner was moved to the right wall of the Chamber, the Wall of Remembrance. There is where it would stay until they died, or became Kage again, which was rare.
When a Kage died, a copy of their banner was placed in the spot of the original. The Original, was taken to the Mausoleum of the Kage, where it resided over their tomb for all time.