You don't need to bring anything other than your clothes & items of a personal nature, just like any top class hotel really. You will need a credit card to register at reception for your onboard spending.
Replied to your PM . . but for anyone else out there
all cabins come with sheets/blankets/towels - so unless you want to really make your cabin homey . . don't worry about those. (as I'm on a ship for a few contracts at a stretch, I do bring my own duvet cover, foamy pillows, blender . . you get the idea ;-) - Uniforms, 'time off' clothes, socks/shoes/underwear for a couple weeks, toiletries for a month and you'll be set. Nice thing about ships is anywhere in the world you are, mostly likely there will be useful ports with grocery and drug stores to stock up, and most ships have a 'slop chest' with relatively useful things.
When I was with NCL - they did send a packing list that was totally useless! It was for a cruise staff . . i.e social host type . . not for a tech - so you probably don't need any 'theme' night wear other than a tux. ANY type of staff position you will need formal night wear. (Tux for boys/cocktail dress or equivalent for girls)
I am a female and I don't wear dresses. I do have a tuxedo. Will they let me wear it? Are techs allowed on all parts of the ship? Or what they seem to call run of the ship? I hope so. I am anxious to see other shows even though I am a lounge tech.
Back then I used to wear what I called a "girlie tux" - nice black jacket and pants and under was a top/vest with rhinestone buttons. Not sure what the dress code is or how well they'd strictly enforce it these days. I'm always on the look out for nice but cheap 'formal' looking outfits. I found a long (to the knees) crushed velvet jacket for $15 that I wear with slinky black pants. The trick is finding comfortable shoes that you can run around the ship with . . and you will have a lot of running around . . esp on a formal night.
Also remember to bring a notebook and write EVERYTHING down - don't know how long your handover will be with the previous tech, but make you take note of when and where . . and equipment patches, band setups, etc as you'll get an amazing heap of info thrown at you and will be responsible for doing it on your own the next time around by yourself.
As lounge tech, you do get the run of the ship, but . . just think if YOU go to a nice resort. You don't see the room cleaners, cooks, wait staff etc hanging out enjoying themselves. You're there to work, and there's a whole 'nother social scene in the crew areas. You can watch the main room shows from the sound/light booth that's in the balcony - and most likely there still are restrictions about staff actually using lounges and restaurants. You'll find that out when you board . . .
No, I didn't mean to give the impression that I want to hang out in the bars with passengers. I really want to see the big shows and to learn how to use more equipment. They told me that there was a career path.