Icon Theme Specification (http://standards.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html) states that /usr/share/pixmaps should be one of the default paths to search for icons. Currently QIconLoader does not support loading icons from this directory.
The spec also says that XPM icons must be supported (although for backwards compability reasons).
In order to load icons from ~/.icons and /usr/share/pixmaps QIconLoader must also implement a fallback to load icons directly from base dirs (as stated in the spec).
I've prepared patches to fix these missing functionalities.
QGenericUnixTheme::xdgIconThemePaths: add /usr/share/pixmaps:
QIconLoader::findIconHelper: also search for XPM images:
QIconLoader::loadIcon: search icons directly from base dirs:
Add QIcon::fromTheme() unit tests: