Icon changer could open a default icons folder
The title says it all — when going to "Properties" of a file, and clicking the icon, the first thing the user could see are some default icons. E.g.: it could open the folder "/usr/share/icons/Adwaita/32x32" by default (or "/usr/share/icons/Adwaita/scalable" if all icons were included in it). There could also be an editable string in dconf and possibly an option in GNOME Files's "Preferences" to change default icons folder path.