Thank you both for your input.
Quote Originally Posted by wysota
LanguageChange is probably not the best example as it is not a custom event but an event sent by Qt to all objects when a new translator is installed on the application and this particular event is handled in QObject::changeEvent.
Apart from not being a custom event it exactly resembles what I want to do with my custom event. I want to have a ThemeChangeEvent upon which QWidgets can reload associated icons, background-images etc.

@ seveninches
The Qt documentation had already hinted me towards reimplementing QObject::event() but I had hoped that this would not be really necessary. Do I really have to reimplement this member in all classes that are supposed to be able to handle the event?