We don't often get to see Primarchs in something other than power armour, do we?
You have my respect for this portrayal; it's quite difficult to capture the individual personality of a character as inherently over-the-top as a Primarch. He looks like exactly what he was to his Legionnaires, everyone's beloved father, level-headed and caring.
My only criticism is the colour. Desaturated, more earthly hues combined with the style of uniform he's wearing are something we've come to associate mostly with post-heresy Imperial Guard officers. Of course, the inverse Omega, the leather straps and the gladius are giveaways, but, well, I had to find something to nitpick!