function randomBackground() {
  var random = parseInt(Math.ceil(Math.random()*2));
  var element = document.getElementById('container');

  if(random > 1 && random < 2) {
    element.style.backgroundImage = "url(/var/img/background/container/1.png)";
  } else {
    element.style.backgroundImage = "url(/var/img/background/container/2.png)";
  }
}