Yes, they have theme nights. Island night is the night of the St. Thomas port stop - lots of fun after late dining on the Lido deck ... and yes, wear island type clothing to dinner. As to the Italian night, etc. - those are just nights when they serve certain foods in the dining rooms. Don't miss the 2nd formal night's champagne waterfall about 11:30 PM. This is held in the atrium - and suggest you get there early - about 11 - to get a seat ... after that you'll probably end up on the staircases - it can be viewed from decks 7, 6 and 5 - the last is where they set it up (over 600 champagne glasses stacked).
I cruise the Emerald Princess, Eastern Caribbean on April 16, 2012
exactly what CruzNut said. The Carribbean Deck Party is a blast. Make sure that you wear something tropical for the evening.
The Midnight Champagne Waterfall is amazing. 95% of the people stay dressed up in their formal clothes for this event. Its the last hurrah of the cruise and you get a chance to party with the staff. Don't miss it.