What is
The main MODEL (hierarchy of different Ticket types) is in "ticket" package. So a separate class diagram of this MODEL would be useful. In addition to the core MODEL there are supporting service layer interfaces in the "ticket" package e.g. TicketManager (the main facade into the ticket MODEL), TicketRegistry (internal ticket cache), TicketFactory (internal factory for vending tickets), TicketCreator (TicketFactory's helper interface for instantiating a particular type of a Ticket), ExpirationPolicy (Ticket's strategy collaborator to define different expiration policies for tickets), etc., etc.
Ideas
Server-side, we can simplify the set of Ticket types we need to model.
There are really only two kinds of tickets. There are GrantingTickets, and there are ServiceTickets. Each of these are a type of (extend) Ticket.
Tickets have two properties. They have a "grantor" property, that is either null or the GrantingTicket that granted them. They also have a String identifier which uniquely identifies the ticket from a large namespace. Part of the identifier is drawn from a large space uniformly at random. This is key to CAS's security.
It's turtles all the way down.