There are 11 stylistic widget variations, these add a unique style variation to the widget: box1-6, title1-5; and various additional structural variations, these affect the layout and metrics of the widget.
Furthermore, you can also add FontAwesome icons into the Custom Variations. You will get a medium sized icon to the left of the title. Suffixes are in the icon-NAME format such as icon-star, as shown on the Typography page.