I can confirm that some icons are missing which are in /usr/share/app-install/icons, but there are also some icons present which are in /usr/share/app-install/icons and not in /usr/share/pixmaps.
I can confirm that some icons are missing which are in /usr/share/ app-install/ icons, but there are also some icons present which are in /usr/share/ app-install/ icons and not in /usr/share/pixmaps.