JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header"></div>

CSS

#header {
border: thin solid black;
    height: 300px;
    width: 300px;
}

JavaScript

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;});

// populate the image with first entry
$('img').attr('src',imgs[0]);


var opacity = 0.1; // change this for minimum opacity
var i=0;
function changeBg() {
    if (i >= imgs.length)
        i=0;
    $('#header').fadeTo('slow',opacity,function(){
        var val = "url('" + imgs[i++] + "')";
        console.log(val);
        $('#header').css('background-image',val).fadeTo('slow',1);
    });
}

changeBg();
var interval = setInterval(changeBg,5000);