I might be tempted to give Hyperborea a bit more Classical flavor by having the various factions use standards (a la the Roman eagle) rather than medieval banners - e.g., maybe Khromarium would use a toad, the Picts a spider, the Kelts an elk, the Ixians a serpent, etc. Maybe the different wards of Khromarium could have different standards (could do double duty as local idols or the like).
Spire banners are a pretty cool idea though.