Ringdom allows you to select multiple ringtones and randomly plays one of the selected ringtones each time your phone is called. It works for both incoming phone calls and also FaceTime calls. Ringdom allows you to choose both user ringtones imported through iTunes and default ringtones stock with iOS.
Ringdom adds a preference pane into the settings app which allows you to choose the ringtones and also enable and disable the functionality.
NOTE: Ringdom currently overwrites any contacts that have a specific ringtone assigned.
Ringdom has been tested on iOS 6 and 7.