Hm...
Let me think about this one for a minute.
I'm thinking your castanets, which are playing the same rhythm as your hi-hats, would probably work better if their pattern shifted over one 8th-note duration. That would offset them enough to give you a kind of call-and-response between them. Panning them in separate directions would give a nice touch to it, too.
That's my only real complaint on the composition of the piece. I mean, I would have liked to have heard more crescendo action going on at some of the transitions, but that's because I'm a sucker for crescendos. Your mileage may vary.
As for its execution, I have no complaints. You've got a good piece going here, Shawn. 9/10 5/5. :D
~Joshy676