Maybe you want to know why I’m talking about SimCity 4 now.
In fact, SimCity 4 allows players to convert a greyscale map to a playable region and The Sims 3 CAW can convert a greyscale map to a world.
SC4 players community released a lot of greyscale maps that we can use in TS3 now.
So if you are a world creator maybe you should visit the ST Exchange|Map section from Simtropolis
Just it requires to resize the STEX SC4 map and convert it into 16-bit greyscale PNG (I use this freeware : Raw Therapee )
TS3 CAW accept 256x256, 512x512, 1024x1024 and 2048x2048 maps and you can choose the height limit between 100, 200 and 300.
STEX Greyscale map: Mars North Pole