Icon designer "Moth" showed a very creative way on together.jolla.com to categorise folders on Sailfish OS.
You find the system icons under /usr/share/themes/jolla-ambient/meegotouch/icons and can replace any existing one. Use a SSH connection (you need to be root) to access the folder. Don't forget to make a backup of those you are replacing - and be aware of what you are doing since you can easily mess up something!
Check out this together.jolla.com link to download those 3 examples and don't forget to support the idea with an up-vote. Direct download of ZIP file here and don't hesitate to show your own folder-ideas.
