We have been on five cruises and I learn something everyday from cruise-chat! I never thought of waiting until the last day to purchase pictures. We end up spending too much money on pictures. When we go on our cruise in November, that is one tip that I'll remember!
I have a tip that may help--be sure to bring some one dollar bills with you. You will want to tip the porter, taxi driver, tour guide, etc. On our last cruise, I ran into a time when all I had in my wallet were twenty dollar bills. Luckily some new friends we made helped me out. So plan on bringing a little tip money!
I know you will have a great time. We were hooked after our first cruise!