Font icons are rad because you can easily style them with CSS. The drawback is that you are restricted to basic things that CSS can do and applying those styles to the whole element.
There are some tricky things like stacking that are cool, but I thought it'd be worthwhile to try directly working with the SVGs for a hybrid approach. I'm going to mess with the Flatties Icon Set to see if you could customize all (well, all of a sub-set) of the backgrounds with a base class.
Popped these up on CodePen if you want to tinker, too.