Teen party ideas....? Help!?!

with that many people, i would say, something like a Bon-fire, so you guys can stay warm. or a dance party ( since you said you had a basement) or a scavenger hunt, hide random items around the house, and make a list of all the items, have a meeting place. and in your case ( with that many people) you can divide them up into 5 groups making 15 people in a group. Or you could do a movie night and you could ask them to bring there favorite movie and you guys could decorate ice-cream sundaes and eat them while watching the movies...
- Hope This Helps, and Happy Birthday!! ((:

my personal idea's

dress up
hollywood theme
famous couples
a colour

themes are sooo much fun and i went to heaps of themed parties in high school, they were the most memorable! i went to a dress up party when i was 17 with about 100 ppl there and it was sooooo good! everyone went to somuch effort and we really loved having something to look forward to :)

You should get a DJ and put music on for people to dance. Have a lot of food out, play few movies in couple rooms so if they're bored they can go watch. In a separate room, they can play games like spin the bottle, serades, hahah(: you know classic games
You should have eating contest ! It sounds kinda gross but guys are gonna love that. with pizza or hot dogs or something. and let your guests create their own desserts. hopeee you have a ton of FUN

i always think that dress up style parties are fun... plus its a great way for guests to strike up conversation with someone they don't know ;) aha
just have lots of crisps and cola and loud music and give everyone some cake on the way home :)

no ideas, too many people