You did a good job filling "empty space" throughout the song, but there's some times when it still sounds a little "empty". If you used violins (or an atmospheric sound font) to play chords throughout it, it might give it more "backbone". By backbone I mean strength, erm, it'll sound fuller.
Also, I just thought a sax solo would sound cool. It could play a variation of the tune. If for nothing than just to drag the song out more.