Take your icon game to the next level. Check out Fonticons, from the maker of Font Awesome.
             

fa-envelope-square · Unicode: f199 · Created: v4.1 · Categories: Web Application Icons

After you get up and running, you can place Font Awesome icons just about anywhere with the <i> tag:

fa-envelope-square
<i class="fa fa-envelope-square"></i>

Looking for more? Check out the examples.