If you want to create a greyscale image like the shell in the first post, you first need to model the object in a 3D modeling program.
Then you need to render the depth map in a rendering program like blender.
http://blendtut.wordpress.com/2011/0...e-a-depth-map/

This method is far more complex than the quick and easy bitmap to 3D model in Aspire shown above, but the results will be far superior. And once you have a 3D model, you can render the depth map from different angles, for a variety of different effects.
Blender is free, btw, and there are many low cost 3D modeling programs out there.