When you complete all the levels of Candy Crush Saga,you receive a congratulations message after you finish the game. After that, you must wait a week to play new levels that are added every week, or you can start again from the first level. There are no other surprises or rewards waiting for you. If you want to continue playing the game, you can try out some of its variations such as Candy Crush Jelly Saga and Candy Crush Soda Saga. These games also have different levels for you to play through.