I find myself continually insta-buying shields with art that matches my banner (even for abhorrent prices!) but I have yet to find enough matching shields for a fully cohesive, professional-looking shield wall. I think the capacity to choose the art design of your brothers’ shields at any armorer’s shop would be a small but terrific addition to this already kick-ass game.
Custom shields would appeal both to players like myself who dig visual cohesion and also to players who prefer more individualized brothers. For example, a player with a brother named “Sigmar the Wolf” could more easily give him a shield with the white wolf’s head over blue background emblem.
The interface for choosing shield design could perhaps be implemented in a similar fashion to the interface for customizing your brothers’ appearance at barber shops. Hopefully this would save you some time in coding too!