Ball/Prom Photography

Hi guys!! im new to this website!stil trying to get used to it. I am a student, studing graphic design & photography. Just been asked to take pictures at a local school prom. I bought myself a portable studio kit. What backdrop do you suggest i get? i like white backdrops myself, but as it is the christmas ball do you think it will be a bit boring? and also, this may sound like a stupid question, what lens should i use for best result?

As goofy as this might sound, how about a gray background then shoot your background light though something that make a blurred pattern on the it, using gels to get what ever color you want.

Jack