What should I do for my 15th birthday party?

My birthday is a while away (early July) but I wanted to start planning now so that I can tell my parents the plans, etc. My parents said I can have a party by the way. My birthday is in Winter so I can't have a pool party or anything like that. I will be inviting guys and girls. The party will be at my house and I think it will be a sleep over. What can we do at the party? How do I keep it from getting boring? Also we don't have a tight budget but it can't be super super expensive. P.S: Nothing too immature please! Any ideas will be appreciated :)