Teens need plenty of activities so often the most successful parties are Mystery Parties, where teams can work together solving a murder or other challenge. A party based on the TV series Survivor is also a popular idea with kids divided into two teams faced with a series of challenges set up on advance. Décor needs to be a tropical island theme (which you can use again next year for a Hawaiian Luau!)
Teen parties are best organized by the teens themselves but parents suggestions would probably be welcomed once a theme is chosen. For example, an Alice in Wonderland party is a great excuse for dressing up and has wonderful opportunities for a costume contest and games – starting with flamingo croquet.