Based on an idea from Michael Penney, I tried the Nuvola Iconset for a replacement of the maybe "less modern" moodle icons. I think furthermore than a new iconset could be less ambiguous in some contexts (guest vs user, settings vs report, etc.).
For the case of Nuvola, I am willing to share my work but I don't exactly no what are the restrictions of the LGPL licence for example for an academic Moodle. Does anybody know ?
Here are two images of my use of Nuvola :

