The Disney Fantasy’s showers (at least on some decks) are essentially identical to the shower heads on the Disney Dream. One of the somewhat minor upgrades over the “classic” ships was the addition of rain shower heads. (As an aside, anyone know if the recent re-imaginations of the Disney Wonder and Disney Magic added similar shower heads?). Anyway, the brand of the shower heads is Hansgrohe and there are places to buy online and probably locally. After trying them in 2011 on the Dream, and again in 2012 on the Fantasy, we did upgrade from a regular shower head to large Hansgrohe. It is quite nice, and something I did myself. Depending on your bathroom configuration, you might be able to do it also, or you might have to hirer a plumber.
Check out the Rain Shower Head – large
Check out the Rain Shower Heads – small size
Or check out the Hansgrohe Store