Storm's Brewing 2.0 introduced a new armor cosmetic system. You can mix and match different armor cosmetics based on the different armors you have worn. There are also 3 new DLC armor cosmetics that you can buy and apply to your armor set at any time.
1. Open your character menu and navigate to the wardrobe button
Armor set shown: Athletic set
2. Select the armor cosmetic you would like to apply.
Note: you can only apply armor pieces that you have worn. Cosmetics do not have apply any bonuses.
Helmet selected: Marauder (DLC)
3. Select Apply Cosmetic to apply just that piece, or Apply Set to apply the whole set (helmet, chest & legs, hands, boots).
4. Apply the set or mix and match the set as you please.
Armor set shown: Marauder (DLC)