Prom/formal hairstyle?

I am going to my school formal this thursday but I can't decide what way i want to do my hair. Do you have any ideas? My hair is a curly/wavy chocolate brown with caramel highlights (sort of like cheryl cole's hair) just below my shoulders. I think i want some sort of updo as my dress is quite low at the back.
It sort of looks like this only my dress is all emerald green and is not a halter neck, it has two straps that gather at the back with a silver crystal thing

http://theselittlemoments.files.wordpress.com/2009/01/brunette.jpg

maybe this, or go with a curl and a cute clip or headband

Hope you look beautiful!

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