I think being able to create your own Sigil would be amazing!
Having your own town, you should have enough money/influence to create your own sigil. Maybe you charge crowns to make one but then once you have it you can spend more crowns to buy banners to hang from your walls or flags to fly high above the troops. Then later maybe you can have your troops match the colors of your sigil, maybe even have them carry a banner.
Along with these aesthetic upgrades you can also add statues and fountains or greenery. That way your city can look as prestigious as you feel when you a march your troops around.
This would add a great sense of pride with your army and town. It would create personalization between armies and allow people to show their loyalty without needing to have a clan tag or something of that nature.