By default, Hyperspaces will display it's own desktop image above the system desktop image. This means that if you have chosen to have your system desktop image change on a time interval, you will not see this change. Hyperspaces allows you to turn off it's own desktop drawing so that you can continue to see the system provided desktop image, and still have text labels and colors for each space.
If you disable desktop images, the color Blend mode controls will also be disabled, and the custom desktop image will not be drawn for the selected space.