Theme 1: Bank Heist - Mission objective is to break into a bank vault and abscond with as much loot as possible.
Theme 2: Access Granted - Mission objective is gain entrance into the computer system of an evil corporation, escalate privileges to open different levels / jackpots. Ultimate wizard mode being to gain super user / root access.
Theme 3: You have a better idea, post in the comments.
What clever rules, features, or game mechanics would you implement with the theme of your choice?