Note: At this point the world is hardly “fleshed out”, and given the innumerable number of islands that exist and the nigh infinite cultures that could potentially exist on each, I’m offering a great bit of freedom with backstory. If you have any ideas at all you want for your character’s backstory, talk to me and let me know. I’ll work with you to come up with something that a) fits the overall vision I have for the world, and b) makes you happy and allows for an interesting character.
Another thing: I encourage a party backstory (including personal ones) and internal roleplay synergy. Not only will this allow for future plot hooks, but parties that can’t play nice with each other tend not to work and lead to an unamusing game. Just DM preference, though; do whatever makes the party as a whole happy.