Have you thoght of maybe doing a Gnger Roger and fred astaire sort of thing...

Maybe a full length with them dancing or a cheek to cheek dancing with some fun creative lighting? my prom pic sucked! It had this awful asteroid belt back ground, gray rug and harsh(bright) lighting.

Something a lot of high school prom photogs don't do is enough headshots or closeups of couples...my two cents---good luck!