To follow these instructions you will need to have a jailbroken iPhone.
Press to launch Cydia from your iPhone Springboard.
Press to select Sections from the tabs at the bottom of the Cydia application.
Press to select Multimedia from the list of sections.
Press to select RandomRing from the list of packages
Press the Install button at the top right of your screen.
Press the Confirm button to begin installation.
Once installation has completed successfully press the large Return to Cydia button.
Launch iTunes on your computer
Select Ringtones from the Library List on the left
Click to select one of your ringtones from the list. If you do not have any ringtones you can learn how to create your own here: Windows, Mac
Press the Command+i keys or right click the selection and choose Get Info from the contextual menu.
Rename the ringtone as RandomRing and click the OK button.
Connect your iPhone to the computer, select it from the list of devices on the left, and click the Sync button to synchronize your device.
Press to select Settings from your iPhone Springboard
Press to select Sounds from the Settings Menu
Press to select Ringtone from the Sounds Menu.
Choose RandomRing from the list of ringtones.
Now whenever someone calls you a Random Ringtone will be played!