Thank you for the feedback! I believe that you should be able to insert a completely new map if you wanted. I would suggest if you wanted to use the islands yet, find only the tiles unused and replace them. I happened upon this technique late one night and I am still unsure if there is a much simpler way, but once you figure things out you are set. Experiment, but make a backup before! I suggest simply adding your sphere tile set below the original, but there apparently have been problems with large tile sets. Good luck, let me know how things work out!