You cannot create your own ringback tones, but you could make your own ringtones from MP3s or other sound files you have handy. Try a site like Phonezoo or Myxer, or look in your phone's manual for instructions about how to save files as ringtones.
I appreciate you taking the time to let us know your comments and suggestions for ringback & ringtones. Verizon Wireless is always looking for ways to enhance our way of doing business to better meet the needs of our customers. Your comments have been forwarded to the appropriate department for review and consideration. Your feedback provides us with the perfect opportunity to hear exactly what you think, and often leads to improvements you will see in the future.