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.
Well, when the AoS miniatures dropped and one was called a Lord Relictor, I just had to have one to put into my 40K Relictors Space Marine Battle Company. So far I have done a lower leg and a whole leg swap to make it 40K and Terminator-esque, the model is already Terminator sized so it was making the jump from AoS to 40K using the distinctive Terminator leg greaves. I have also added a power haft to the Thunderhammer, a simple cut and shunt of the original bits.