you can add anything you want as a ringtone, dont remember exactly how on stock but its fairly simple no matter what. usually its just a matter of using your music player or the file explorer and holding down on whichever one you want then clicking use as ringtone. technically you could just steal the ringtones from the venice, but i prefer to take my mp3s and chop them up in audacity then toss them onto the phone. and if oyu want to be really fancy about it, you can use audacity to convert them to ogg format, make sure to give them a title in a meta tag, and toss them into the /system/media/audio/ringtone or notification or whatever you want to replace, that will add them to the actual system menu as long as you made sure to edit the meta tags