Code:
.username--style3:before { // Change the number 3 by the number of the user group you want.
font-family: "FontAwesome";
content: "\f132"; // Change the unicode (f132) by the one you want to find on the site: https://fontawesome.com/v4.7.0/icons/
color: inherit;
padding-right: 4px;
display: inline-block;
}Add to extra.less