The banner can either be just a reliquary befitting the Lord of the Relictors or the Banner of the Emperor Ascendant for gaming purposes if he is used as a Chapter Master, or maybe with the skull helm, I did think a Chaplain, but I already have a Terminator Chaplain so the Chapter Master won out. I've swapped a few trinkets for a Termie Cross and an Imperial Aquila, next up is the fiddly fitting a Crux Terminus to the Shoulder Pauldron and adding a few skulls in place of Sigmar hammers. And then maybe a Storm Shield to make him more survivable? Perhaps The Shield Eternal? The Thunder Hammer replaces his standard issue StormBolter. The Banner or Shield replaces the standard Power Sword.