The archetype uses the twitter bootstrap theme. When you download it, it contains a glyphicons-halflings-regular.woff2 file. That is not included in the archetype. But when you start working with the icons, you get a warning that the .woff2 file is not found.
Please add this file to the /plugins/skeleton-package/src/main/resources/instructions/bootstrap/fonts folder in Essentials.
If you have time for it, consider upgrading to the latest version of the theme at http://getbootstrap.com. Currently it is at 3.3.6.