*BUMP*
Addition: Husky's method.
Select a random island map to work from (and put objects on '10').
1. press

to see the map with objects on it.
2. RIGHT-click

and LEFT-click on

again. You now get a message warning you about colour loss. Choose 'yes'. Both the original map and the objects on it are now shown as regular 'white'-terrain.
3.LEFT-click

again and you will see that the objects are now placed on top of the 'fake' objects that are now part of the terrain. The map is now quite a bit more complicated than it was when you first selected it.
Use the 'reseed' button to randomize the objects 'till you are satisfied.
Visual aid:


N.B.: It is ESSENTIAL that you use a terrain-type with smooth surface for the fake objects (as any grass on top of it will be turned into solid terrain as well). Suggestions (from the top of my head):
Pirate, New York (see above)
Paint, Cheese, Music, Screws, Beach, Clocks, Pirate.Medical-theme can also be used, but the objects aren't good to use as fake ones (the needles, hospital beds, etc. will feature a lot of narrow lines and spikey hooks). Better use Paint or New York, as both have pretty big and very solid objects.