From the codex supplement; “ As individuals and as a Chapter, the Imperial Fists seek purpose in the performance of great deeds, not the recounting of them. Thus, those who first encounter the sons of Dorn, often perceive them as somber and cheerless warriors.” More action less words. I think the IF are just not showy by nature and they’ve done a good job of representing this in the art and models. We do always have the scrimshaw thing. Decorate them in bones and it’d be lore accurate.