Ok i'm not sure if this is a known feature, but i just 'discovered' it tonight (while procrastinating on a paper, woohoo).
Try holding down command-caps lock-3 when the visualizer is turned on. you can switch between different types of visuals within the default visualizer by holding down either 3, 4, 5, 6, 7, 8, 9 or 0 (and command-caps lock). pretty cool.