RUGreek, lol.
I go to a Christian school too (Catholic), and you might not want a Christian band (hey, I love Christian music - I'm listening to Chris Rice right now) for your formal. Not everyone there is gonna be a Christian, or is gonna like that kind of music.. etc. Cute idea though; the music is great.
Hey, I have an idea that would be fun - why doesn't everyone throw out your prom ideas so we can get new ideas (rather than mixer ideas)? Not only would they be new, they would be "clean" (since they're high school-sponsored).
Junior year, our theme was "Black and White Ball". Supposed to be classy, but it was boring, in my opinion. If you do use this, use your sorority colors and deck the place out! It could be cute, if done right.
We did "Viva Las Vegas" (casino theme, not Elvis theme

) senior year - covered tables in green felt and glued cards to them and put poker chips in the middle of the tables, gave out glowsticks, had a cute sign with light bulbs around the border, and our pictures were taken as if we were at a wedding chapel (they gave us a veil, top hat, and bouquet to use in the pictures, taken in front of a big silver bell centerpiece thing! It was so cute). So much fun!
Tau Love, Marly