Something strapless would look darling on you (:
A lace-up back would be nice, if you have a REALLY big butt, go for something in two pieces, a corset top with a skirt, because that will take the attention away from your butt. Or you don't really have to, because I don't think your butt is that huge. It's nice and shapely. (:
Your hair is pretty good how it is, just on the day you can either get it styled at a salon (like Grey Rainbow said) or a couple days before, see if you can style it on your own, and you can save the trip to the salon.
I think it would look great just with some gel to bring the layers up, then flipped outwards a bit? And some clips. Nothing too kid-y though, maybe a sophisticated flower of some sort.
I think you would look great in blue.
Nothing too pastel, but like a bright turquoisey blue would look really good.