First we'll need to add an image layer. The image layer expects the name as the first parameter (like other layers), the URL of the image next, then an {OpenLayers.Bounds} object specifying bounds of the image, then an {OpenLayers.Size} object which contains Width, Height pixel dimensions, and finally an optional options object.

var image_layer = new OpenLayers.Layer.Image(
  'Wallpaper',
  'http://us.starcraft2.com/images/wallpapers/wall3/wall3-1920x1200.jpg',
  new OpenLayers.Bounds(-180,-112.5,180,112.5),
  new OpenLayers.Size(1920,1200),
  {numZoomLevels:7, maxResolution:.625}
);

Let's create another image layer now. We'll set the opacity to 20 percent and make sure it's not a base layer by setting isBaseLayer: false in the options object. We'll also be using a different URL:

var image_layer_2 = new OpenLayers.Layer.Image(
  'Wallpaper 2',
  'http://us.starcraft2.com/images/wallpapers/wall6...