Actually, I guess it's traitors and loyalists.
Mortarion? Though scarf strikes me as a Corax thing.
Perturabo? The apparent autism is the only clue.
Which I guess makes the one with no defining features Horus.
I'm going to say Corax for the resting bitch face coupled with not being Lion.
Sanguinius, I guess, even though the hair makes me think Grecian influence.
Ferrus Manus obvious
Who the fuck is sports girl? Is it Vulkan because he's black? Is Dorn athletic?
Is glasses one Dorn because he's analytical?
Is hair-wings one Guilliman because it's funny for him to be a ditz?
Is Khan supposed to look stereotypically Asian among manga-styled characters?
Lion at least is also obvious