On page 21 they detail a full overview of Spartan concept art. The next pages show off the Mark VII and their variants, but the fact that they have 15 separate images of the Mark IV showcase each multiple variants of customizables. Ranging from Helmet Attachments to Knee Guards.
Granted indeed it is all concept art, but the vast majority for the Mark VII concept art armor cosmetics are confirmed to be in the game and the Dieselpunk Fractures armor core is showing that their concepts are final products.