If you want to extend your stay or combine it with some cultural activities, the Hague is a great location! The city has a number of excellent museums, galleries and other attractions, and is even conveniently located for trips to the beach. You could also consider visiting other parts of the Netherlands, such as Amsterdam, any number of beautiful, sandy beaches, or the Veluwe national park. The Netherlands is so small that it's easy to see a lot within a short space of time.
Want to know more about the Hague or the Netherlands more generally? Try this site.