Edit in JSFiddle

var img = document.getElementsByTagName("img"),
    total = img.length,
    i = 0,
    fn = function(){
        img[i].style.opacity = 0;
        i = i == total - 1 ? 0 : ++i;
        img[i].style.opacity = 1;        
    };

img[i].style.opacity = 1;
setInterval(fn, 4000);

<img src = "http://www.fondosblackberry.com/user-content/uploads/wall/mid/32/Paisajes_manu_peru.JPG" />
<img src = "http://www.fondosblackberry.com/user-content/uploads/wall/mid/54/paisajes_de_peru.jpg" />
<img src = "http://www.fondosblackberry.com/user-content/uploads/wall/mid/6/Autumn_day_river.jpg" />

img{
    opacity: 0;
    position: absolute;
    box-shadow: 0 .5em .5em;
    border: .1em lightgray solid;
    border-radius: .5em;
    transition: .75s;
}