Paint.NET :: How To Add Depth To Human Figures

How to make a human figure look like it has REAL depth.
 
If you have ever seen any of Ken Burns documentaries he uses a lot of pictures in his films from the past, but some of the figures or people in these stills appear in depth in such a way that they do not look flat.

Instead when the camera pans the picture they appear to be almost three dimensional inside the still. You can almost see in his stills there is a curvature to the outline of the figure. Their heads and bodies look as if they are inserted into the picture.

I have the removal of the background in the image down well enough but I don't know how to make the figure appear as if it is 3 dimensional in the new background. I wish I had a link to add here of his work as an example.