The Event Bazaar offers a lot of units depending on what events are currently on-going. However, there are permanent categories in the event bazaar that offer a variety of units, spheres and others. Examples of these are the Guild Relics and Brave Insignia categories.
Units found in both of these categories are listed under the "Units Tab".
Unit alternate art can be found in the "Other Tab".
Not to be confused with an actual unit; Alternate Arts can only be used when you have the unit of that specific art. If you buy an alternate art you will be unable to use it until you have the actual unit.
For a simple guide on how to view a Unit Alternate Art you can read this article here: How to view unit alternate art?