Demi, those are sort of my thoughts with the whole thing. One thing I know from reading multiple books on the Knights-Errant of Brettonian, is that no campaign streamer or banner is too gaudy, ornate, or impractical. The better to rally forth the peasantry when they bear witness to the mythical figure of the Green Knight weaving through the enemy ranks with the same ease that his streamer dances provacatively through the mid-morning breeze.
Ten, the Fluer-de-Lis symbol is also in keeping with Brettonian heraldry. Also, Ten, if you go with a downsized streamer and use ivy on it too as some suggest, I'd go with a different kind. There are several manufacturers, including the Warhammmer basing kits, that sell a brass etched ivy that is simply a single vine that you could wrap around it. Just a thought for additional visual interest. Someone once told me small medium and large need be represented.
Cheers, I don't envy you your tough decisions.