Luggage and bags:
Take an extra bag for when you go home...you will probably buy a few things while in Vanuatu... ;)
Clothing/Shoes/Weather Gear: Light and casual clothing is about all you will need. Plus maybe one pair of long pants and a light jacket. Also take good walking shoes and some wet socks/surf socks if you have them.
Toiletries and Medical Supplies: You should bring most stuff from home but you can buy things at the chemist and supermarket (at a fairly high price).
Photo Equipment: Take lots of film or huge memory cards! And a tripod will come in handy too...
Camping/Beach/Outdoor Gear: Insect repellant with DEET in it is a must...as well as sunscreen and lots of it!
Clothing/Shoes/Weather Gear: Vila and its cruise-port Port Vila had been the hottest placest that I came to on my cruise to the Fiji Islands, Vanuatu and New Caledonia. At lunchtime it was much too hot to take a walk around and the heat was also full of humidity that made you soaking wet within just a few meters walk. So you better cover your head and skin and walk in the later afternoon, like I finally did it.