Customization cases can be purchased in the Shop. Sometimes they can appear as a season or event reward as well. Each case contains a random number of sprays and one random skin, trail, or avatar. If you receive a skin/trail/avatar that you already have in your collection, then it is converted into sprays.
Attention! You can receive a skin for a ball that is not yet unlocked.
You can find the full list of skins in Skin Collection. To reach it, tap on the customization case in the Shop, then hit the 'Skin Collection' button.
Sprays are the in-game currency. You can exchange sprays for new customization items: avatars, skins, or trails. Not all items are available for exchange.