"Font Awesome" is, surprisingly enough, not just icons but also a font. And while you can apply fonts manually to the graphs, you cannot do it trough the skin system. Seems "customization requirement it will not be considered as an ER" they did give a workaround (Doc ID 2033643.1) but since it requires client side changes…

You can import a font in your custom style / skin css, but that only gets you halfway, it won't work for the graphs for example. I would expect changing a font to be a basic customization feature.

The official documentation on how to deploy a custom style or the tons of blogs only cover how to add a default system font, there is no documentation for making a custom font available from BI ...