A new map style was added for the Virtual Earth v6 Map Control API which allows you to have shaded relief maps.  For example, here is a screenshot of the traditional road map style (VEMapStyle.Road) in Virtual Earth over the Grand Canyon:

Here is the same location using the new shaded map style:

To use the new Shaded map style, you just need to pass the VEMapStyle.Shaded property to the LoadMap call at init:

map = new VEMap('myMap');
map.LoadMap(new VELatLong(36.291883, -112.806930), 12, VEMapStyle.Shaded);

or you can call SetMapStyle with the shaded property:

map.SetMapStyle(VEMapStyle.Shaded);

Here's a link to a working example showing the new shaded map style:

Virtual Earth API Shaded Map Style Example