I was working on my Crimson Fists the other night and kept thinking that something was missing. How can I add something that would make them just a tiny bit different than your run of the mill space marines. So I figured that I'd add a little detail here and there on ever model. For me, it does two things. First, it makes them different than generic marines. And second, it makes each model unique.
In my research, I did learn that the Crimson Fists had conducted joint operations with the Black Templars, another chapter descended from Rogal Dorn. During the Declates Crusade, battle brothers from both chapters exchanged iconography as a symbol of unity. So, my plans are to display that exchange on some of the models. I'll paint a templar cross or use some of the black templar shoulder guards throughout the army.
I'm kicking around a few more ideas and using scripture and hand painted tactical arrows, just to change things up a bit. So let me know what you think.