As far as the archipelago idea goes, the Saga of Recluce uses it for the map.
The fantasy part was active gods and titans.
And other things the gods put into the world to screw with the people that worship or are champions of their opponent gods
Bah, I thought you were talking about the non-standard map bit there.
Concept: Recyclable Time
Desxription: The nature of time is such that a single moment or day or other duration can be lived over and over again WITHOUT resulting in a Groundhog Day style loop. Instead it merely results in one day being largely the same as the next, and a slowing down of aging, social change, and things like that.
Source: Discworld
I don't follow. Mind explaining some more?
Concept:Magic as order vs chaos
Description: There are two (well, three) types of magic. One uses "order" to strengthen materials, help shape crafts and generally make things more orderly. This can even go so far as being used to manufacture steam engines. Then there is chaos magic, which is the more traditional fireball throwing, shit exploding, scrying-type magic. Most people who can do magic are only capable of one or the other. However, there exist those who can use both in balance, making them the most powerful wizards of all, allowing them to even extend their lives almost indefinitely.
This order-chaos interaction underlies everything in the series, and takes are rather taoisst philosophical turns in many of the novels. At one point so much chaos is created that the most powerful ordermages in the world have to work together to encapsulate it and essentially destroy all latent order and chaos in the world, resulting in magic basically dying.
Bonus points for awesomeness: At one point an armada of ships is destroyed via lava being released from under the ocean and burning all of them.
Source: The Saga of Recluce