No way to automatically do it, unfortunately. A hack would be to set the screen saver "How often" to "1" (second) and the "For how long" to something huge, like "99999" (seconds). Of course, the drawbacks are that every screen gets inverted colors, and when the screen changes (say, from the Tournament screen to the Player Rankings), it will go back to un-inverted for 1 second.
Otherwise you'll have to manually do it. I can invert the background image for you, but you'll also have to set the font colors of basically everything. I might be able to do that, too...