This addon allows you to create a waiting form after the tickets have been sold out so that people can reserve one in case one of the attendees cancels their reservation. People on the waiting list are moved to the main list based on the priority of their reservations.

CookAndMeal – Food Blog and Recipe WordPress Theme
CookAndMeal is a simple, feature-rich WordPress theme for food bloggers that makes it simple to deliver thorough, personalized, and interactive recipes that are sure to make people salivate.