Class is an extremely simple and elegant design that allows you and your visitors to customize the look and feel subjectively. There are also presets that will allow you to set predefined 'sub-skins' for quick use. Some presets might include a Halloween design, perhaps a game or game console, etc.
Backgrounds and textures can be added quite easily as well. With just a few changes, you can set any color scheme you want easily from the control panel.