How to add the background css into this jQuery? [duplicate]

You can do it without img elements, using backgound css property, like here:

var img = 0;
var imgs = [
    'http://www.istockphoto.com/file_thumbview_approve/9958532/2/istockphoto_9958532-sun-and-clouds.jpg',
    'http://www.istockphoto.com/file_thumbview_approve/4629609/2/istockphoto_4629609-green-field.jpg',
    'http://www.istockphoto.com/file_thumbview_approve/9712604/2/istockphoto_9712604-spring-sunset.jpg'
];
// preload images
$.each(imgs,function(i,e){var i=new Image();i.src=e;});

var img = imgs[0];


var opacity = 0.1; // change this for minimum opacity
function changeBg() {
    $('#header').fadeTo('slow',opacity,function(){
        $('#header').css('background-image', 'url(' + img + ')').fadeTo('slow',1);
    });
}

setInterval(changeBg,5000);