Just one thing though...  True you can use an image to make a terrain, but you forgot something.

"Any ol' image" != "heightmap"

Of course you could use it as a reference and paint a grayscale heightmap over it on another layer in your favorite 2D app.

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Barbequed Pixels?

Your friendly neighborhood Wings3D nut.
Also feel free to browse my freebies at ShareCG.
There might be something worth downloading.