There are specific amount of units in the game that have a Unit Alternate Art. While some units have their alternate art immediately unlocked when you obtain that specific unit, other alternate arts are obtained through other means such as Strategy Zones, Limited Time login campaigns and through purchasing in the Event Bazaar in exchange for specific tokens.
Obtaining or purchasing an Alternate Art of a specific unit does not mean you get that unit. You will still need to have that unit in your unit inventory in order to view the alternate art.
How to view alternate art:
First, once you have the unit and have bought or obtained the alt. art you can view it at the "View Units" tab.
By selecting the unit which has the Alternate Art, you will be able to select between unit art by pressing the "Switch Display" button found on the top right corner of the unit profile.
Once you have done all these steps you can freely chose between which character art you would be using.
• Alternate Art does not change the battle art of units
• Each duplicate unit with an alternate art will always be using the original art of the rarity of that unit. Each duplicate unit can also be using different character art depending on what you prefer.