In Ring of Elysium, you unlock new outfits by purchasing them or by reaching new levels. To change an outfit, go to the Appearance tab and then click on Character.
Here, you can equip or remove: a hat, gloves, goggles, masks, t-shirts, coats, pants, and boots. Clothes don't affect your character's heat during a match.
You can also unlock a special character. Their outfits are all pre-made. Check one of the pages to learn how to unlock these adventure characters.