To customize the header of Titan 2.0, simply create an image with the dimensions of 948 pixels wide by 250 pixels tall, name it header-bg.jpg and put it in the _global  folder, overwriting the existing image. The skin will automatically add the image for all sections and put the inner shadow over the image you uploaded (though that can be changed or removed by modifying the box-shadow properties in the header tag in the stylesheet).