Definitely goes on too long without more happening. Throw in a melody over that and it should get things rolling. Just be sure not to get trapped on that vamp forever.

If you're actually going to make this into an orchestra piece, you'll have to disperse the notes of the melody and harmony among the different instruments. Each one has a different range and feel for their sounds so you ought to definitely study up on the different instruments. If you just want to cobble something together that uses the orchestra instruments, I would try giving those chords to the strings (or leave it on organ if you like), then come in with a horn or violin on it's own for a melody or theme that fits the atmosphere. Hell, you could even leave that to the organ and have the strings playing slow atmospheric music and possible swell in volume then take over or add to the chords once the melody enters.

Just a couple ideas that came to mind.
Quote by DiminishedFifth
Who's going to stop you? The music police?