I'm swiping this from something I read here I think, but it was a Panhel theme, not a specific sorority's, so I feel it's ok!
On the front left they had their house and the rush date or school or something, and the back had two girls laying on the ground looking up at a starry sky with all the houses letters in them. The slogan was something like why wish it when you can live the dream or something like that. So maybe you can do something like, "wish on a star, and your dreams can come true - NBO" and make a starry sky and have 'constellations' in the form of your letters? Or something to that effect?
And maybe at a rush event do something with rushees astrological signs, or decorate like that or something? Just a thought...
Good luck, Corina! We are all rooting for you and NBO!