I wonder why nobody propsed most badass knight order yet - Knights of Morr. Grim, fear - striking knights wearing black plate armors. Defenders of living and dead realm a like, guardians of temples and graveyards, silent and efficient knightly order. They are also known for their usage of firearms so witch hunter class would blend in, alongside with warrior priests who accompany the brotherhood in their ever vigilant duty against undead. I find that way more appealing than most other knight orders
As for uniforms - simplicity is beauty. Finding some plate armor that would be both heavy and protective, yet not so gold-ornamented isnt easy task but is doable. Colors - main black , secondary red. Skulls everywhere where its possible
BTW. When i finish farming that damned Ruin set ill start with visual guide to KotBS since i belive i have vast majority of equipment avaible to that class, including influence gear from both rvr and pve, all rvr sets beside annihilator, lair equipment and all or almost all green items. And hell lot of weapons to choose from :>