just as a tip: enable all fancy graphics when you create such showcasing screenshots, it becomes much more attractive that way
Also, as the creator of the original map, I would like to make a few comments on the map design :
I haven't try to play it so I can't comment on how the maps plays but it looks as if the two players on the most northern island have much less resources than the other two.
On the upper two islands you can see quite a bit of texture tiling (especially in the flat areas), you might be able to take a few clues by looking at the original island and see how I blended the textures together and got rid of most of the texture tiling
The small island in the northwest could do with a bit more effort I think, try to come up with some fancy spots and terrain features to make it more interesting! (but don't overdo it, keep it natural and realistic :P)
Other than that, a nice idea for an extension!