wowah, what a boyfriend.
This is something my friend did a couple of years back.. he told her to a movie. sounds common, but he reserved the seats that made up a heart shape... and apart from two seats in the middle for the couple, the surrounding seats have roses/teddybears on them, so upon entering the theater the girl (and everyone else!) would be able to see the heart shaped design and the two special seats in the center =)
of course, its better u tell the cinema ushers beforehand so they can help you with it, or even let ur friends enter the cinema a little earlier to prepare. Good luck!