A method for easily stacking multiple icons. Use the fa-stack class on the parent, the fa-stack-top for the regularly sized icon, and fa-stack-bottom for the larger bottom icon. fa-inverse can be used as an alternative icon color.

{% highlight html %} fa-twitter on fa-unchecked
fa-flag on fa-circle
fa-terminal on fa-sign-blank
fa-camera on fa-ban-circle {% endhighlight %}