As for the port itself, it sounds a little empty: there's no echo or panning. Since you've got 4 empty channels, you've also got room to add some fake-echo, where you copy another channel's data but with a slight delay, or you could chord some of the main melody's notes to make them fuller, or alternatively even stack two channels with the same notes but different samples, with potential tuning differences, to achieve a unique sound. Speaking of samples, I believe the instrument choice could also be better: the @2 doesn't work very well, especially without echo, and the @3 feels way to empty and rigid for the backgroud notes.
One last note, I notice you used tags which aren't from the official tag list. Please make sure to only use tags from the official tag list on the Submit File page when submitting things.