December 2, 2015, 10:41 am - James Farrer
This is mostly for my personal reference but here is the info on what icons are available as taken from the ServiceNow Community Forum. Thanks to Shahid Shah for putting this out there.
What I can advise you is that the symbols are based on Web Fonts (in this case retina_icons) and the styling is managed in the internal CSS. So you are restricted to the available character set by using the icon-name format for the class name: