I cant do better than the map you have found. I can only point you at some of my free tools. There is an instant island generator:
http://www.viewing.ltd.uk/cgi-bin/vi...nstant_islands

and a program which views these in 3D:
http://www.viewing.ltd.uk/cgi-bin/vi...dragons_flight

and either allows you to save out an image so you can have flat green or shaded green. But if you wanted rocks, trees and so on then you would have to work it a bit.