Hi Harald!
The section icons are made by Michael Madsen and is a part of his old (2002) MMICONS Blue set:
http://mmicons.deviantart.net/mmpreview/aqua.jpgTo download icon files go
to the website, click the "MM Icons" link, then click the button number two from the right next to the text "LOAD ICONS SET'S HERE" and choose "MM-AQUA" in the bottom. It's an old flash site, so you can't link :-(
There are no guidelines, other than I'm pretty sure these icons won't survive the v4.0 refresh next year - but until then... :-)
/n
Jeeeez, did I really start this :-)