Storm's Brewing 2.0 introduced an armour cosmetic system. You can mix and match different armour cosmetics based on the different armours you have worn. There are also DLC armour sets which you wear as they are, or mix and match with other cosmetic items.
1. Open your character menu and navigate to the wardrobe button

Armor set shown: Athletic set
1. 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)
2. Select Apply Cosmetic to apply just that piece, or Apply Set to apply the whole set (helmet, chest & legs, hands, boots).

3. Repeat this step until you are happy with how your armour cosmetics look.

Armor set shown: Marauder (DLC)