Here it is my /etc/gtk-2.0/gtkrc:
gtk-fallback-icon-theme = "gnome"
Note I commented gtk-icon-theme-name="Mist" to make rainlendar work.
/usr/share/themes/Clearlooks/gtk-2.0/gtkrc is the standard one.
Gnome and XFCE users have gtk-icon-theme-name set by gnome-settings-daemon or xfce-mcs-manager.