I didn't spend much time shopping on the ship. I remember a jewelry store, liquor store, clothing store with a wide variety of items....pool wear to evening wear. I would definitely save my shopping dollars for the ports (St. Martin and St. Thomas!!!)
There is also a nice perfume store, prices about the same as the ports, so if you run out of time, you can always pick up some onboard, still duty free :-) There is also a store for the "basic" cruiseship t-shirts etc.