There's a lot of good stuff here. As ProjectSpam said, the intro is really great. The layering of the strings/pads is haunting, as are the chimes delivering the original theme's counterpoint. The whole piece feels very much like an ethereal mist glittering with pinpricks of starlight.
The addition of the piano echoing a reminder of the famous prelude is a nice touch, but the instrumentation doesn't quite work for me. It might work if you had a better piano, or it might work on a different instrument. Right now, the piano just sounds weak and fake compared to your other instruments.
After the first minute or so, we've heard pretty much everything there is to this piece, we've got strings and ethereal voices and tinkling chimes and piano, but they all pretty much to their own thing. The voices in particular become a bit grating. They start wonderfully, but they go on for too long, become too prominent, and they never changed tone. There's nothing wrong with a drone of course, but this one isn't working for me. It goes from been really subtle and lovely to beating me over the head with a bat that says "Look! I'm mysterious!" More subtlety please!
Don't be afraid to step a little further away from the original work. Let the pads explore some different harmonies. Play with different sounds and try different layering effects. Maybe even throw in some nonstandard percussion effects. As it stands, the mystery wears off to fast, so keep us on the edge of our seats.
Looking forward to hearing more!