Tipping in Ashmore and Cartier Islands is probably the last thing on your list of things to worry about. In fact, if you got to the island as a tourist you would have a story to tell! The island is owned by Australia and is an overseas territory. It is a protected island so you won’t be able to visit unless you work for the government or are a fisherman. A permit would be required by the Australian government.
If you do get the opportunity to go the tipping wouldn’t be a concern! There isn’t any services on the island and it is uninhabited. Have fun though! Its a once in a life time experience!