um well you have music...
um food, teenagers love food!!
a dance floor? i know i love to dance and my friends do to, so that could be a possiblity?
for decorations you could put up like Christmas lights around the house or where ever you are having the party
but i think music, a place to dance, food, and alot of people would be great.
but idk, I'm going to be in Disney on my 16th birthday with my best friend.
but one of my friends is going take a couple of her friends to a hotel for like 3 nights in the City and wil go shopping and do other things.
I hope I helped...