Julian Ridden has provided some icing on the cake that is the Bootstrap based Essential theme for Moodle. Now themes that follow in the same vein and utilize FontAwesome can also apply this filter and have a library of easy to implement icons on any page on the Moodle site.
The FontAwesome icon library is pretty extensive and easy to use, requiring only brackets, correct syntax and the right icon name to deploy quality icons right on the Moodle page. To see the full library check out http://fontawesome.io/icons/
Download the required theme, Essential here: https://moodle.org/plugins/view.php?plugin=theme_essential
Download the filter here: https://moodle.org/plugins/view.php?plugin=filter_fontawesome
Or find both through your Moodle 2.5 addons menu when logged in as an administrator.