var x = -1, backgroundImages = [
    "/images/desktop-year-of-the-tiger-images-wallpaper.jpg",
    "/images/background-gmail-google-images_FG2XwaO.jpg",
    "/images/beautiful-sunset-images-196063.jpg"
];

function changeImage() {
    setInterval(displayNextImage, 10000);
}

function displayNextImage() {
    x = (x === backgroundImages.length - 1) ? 0 : x + 1;
    document.body.style.backgroundImage = "url('" + backgroundImages[x] + "')";
}