The w3-ul class creates a basic list:
The w3-border class adds a border around the list:
An example of how to add a heading element inside the list item.
The w3-center class centers the list items:
The w3-hoverable class adds a grey background color to all list items when you mouse over them:
To close/hide the list items, click on the "x":
You can combine w3-ul and the w3-bar classes to create an avatar list: