The only solution for a random ringtone now is Random Ringtones, MortScript by oblyvaeon. Koterpillar made a simple application to do just that – randomize your ringtone. It scans your storage card (or any other location you specify) for music files and every time after an incoming call your ringtone will become one of those. Unlike the mentioned script, it does not require to be running all the time, so there is zero CPU and memory usage.

Features of version 1.2.1:

Select many folders to get ringtones from
Exclude some ringtones you don’t like in those folders