rklennie:
My team and I work with waitlist candidates all the time. Unfortunately, there isn't a ton you can do.
Get in touch with the AdCom and see if they will provide any feedback specific to your application. That might pinpint a specific area you can improve on (e.g., GMAT) that just may make a difference.
Other than that, a standard letter of continued interest can be helpful. You should document any positive changes to your profile as well as new ways you have engaged with CBS.
Lastly, if you happen to know someone influential at CBS (or in general) who is willing to write a letter of support, that could be a potential game changer.
Waitlists are incredibly frustrating and inflexible, but pull every lever you can, have patience and maintain hope!