Try a more casual look, too. A polo shirt, or perhaps a nice sweater (sweater+kilt is a good combination.) A lot of people don't go full-out formal for their senior picture, but the picture can still be excellent.

One guy I knew (not from my school) handed in a picture of himself in a full and correct reproduction suit of late 15th century Italian armour, on one knee, helmet under one arm and sword in the other. The next year the school implemented a strict shirt-and-tie policy. So get your kilted pic while you can!