The visual style also controls the display of backgrounds and shadows in the viewport.
You can use a solid color, a gradient fill, an image, the sun & sky, or an image-based lighting (IBL) map as a background in the viewport in any 3D visual style, even one that does not shade objects. When Background is set to On in the current visual style, the background is displayed.
To use a background, you can
Shaded objects in a viewport can display shadows.
The lighting in the viewport must be from user-created lights or the sun for mapped object shadows to be displayed. Where shadows overlap, they appear darker.
Displaying shadows can slow performance when viewing a 3D model. You can turn off shadows in the current visual style while you work and turn them back on when you need them.