I picture the banner as being much more Medieval. Dark. Crumbling. Gothic.
The Kingdom is the last bastion of Order and Civilization in a land long since abandoned by Britannia and its King. It is a land choked with the blood of the fallen; whose restless souls cry out for vengeance. It is a land torn asunder by violence and a war that will never end.
Dawn occupies the harsh and wind-swept region at the Crown of the Old World; known to some as the Hyperborean North. It could be compared to a Village in the Scottish Highlands or Scandinavia. Something one could picture being in the Braveheart or the Mists of Avalon. To the South is the Borderlands and the Nordmark; where bleach white bones and the burnt husks of war machines (I wish) mark the site of battles between Dawn and the Vanguard of Na'Krul. To the North is the Black Coast; where the Gulgeth and the Savage Tribes battle for dominance in a genocidal campaign of racial enemity. And to the West juts the snow-capped peaks of the Mountain of Steel; where the Stygian crypts of an ancient line of kings has become the hideout of Highwaymen and Murderers. The inhospitable terrain is often softened with the blood-churned mud of Barbarian invaders, Pirates, and foolish would-be conquerors from the Britannian Kingdom. It is a harsh place of war and tightly-knit bonds where strength and cunning are key to survival. It is a land of savage gloom that offers no comfort to its hardened citizens.
The region was once home to the Varangians and the Amazoni before Lord Cross arrived to carve out a Kingdom of Order; one not beholden to the corrupt and scheming Britannic Council. While Dawn was once a City of Sorcerers and Thamaturgists, trapped in the Ethereal Void; the majicks of the elders are no longer favored amongst the common folk who have watched their most talented wizards fall under the spell of Na'Krul and Ivy Shadowfare.
What would I suggest? Something that reflects this tale. Not something cheery and devoid of context; but something that reflects its history and lore. The Mausoleum of the Thamaturgist.
I would recommend something very similar to the crumbling ruins designed for Aryslan on Chesapeake. The crumbling remnants of a tomb built during a previous epoch. The walls would be decorated with vines and creepers. The outside would possess two of the Veteran Reward Portal Orbs atop a dais and flanking the doors; but these would be darkened to reflect the Moonstone that was broken and later recovered by Desmond Cross. And in the center would be a Sarcophagus.
The sarcophagus would be watched over by three (warrior) statues carved from a dark bluish stone; immortalizing the Three Elder Hierophants that once led Dawn and who later passed the mantle onto Desmond Cross. And nearby would be the Banner of House Cross; blue and black with a golden harp in the center.
I don't see much need for thrones. The King and Queen hold court in the Dawn Palace; so I don't see the need for another set.
But that is just my thought.
