Have you considered using some of the Byzantine Ikons as reference for banners- I did print one off showing the Archangel St Michael for use as a Cossack banner.
I did some Cossack banners for a friend (years ago) by cutting out the
pictures of CD covers from a catalogue. Classical music ones provided some
very nice religious Icon type banners.
Yeah, I've got a quite a few taken from mosaics the 6th CE Eastern Roman Empire saved and many are already being worked on- well experimented on might be more accurate

. Just 28mm scale to start off with. the 400mm x 400mm stuff can wait until later

If you have anything from the 6 CE please email them to me George.