We currently load some JS and CSS assets from the web, for example in the Main layout:

{{ '//netdna.bootstrapcdn.com/font-awesome/4.3.0/css/font-awesome.css' | stylesheet_link_tag }}
{{ '//ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js' | javascript_include_tag }}

Some customers have a network setup that doesn't allow getting these assets from the internet. So, for on-premises it would be good to build the assets into the images.

/dev notes

admin portal work has been done (2.7)
dev portal work not