var footerImage =
{

  images: [],

  initialize: function() 
  {
    for (var a = 1; a < 9; a++) 
    {
      this.images[a] = new Image();
      this.images[a].src = 'img/bottom_' + a + '.jpg';
    }
  },

  display: function() 
  {
    document.getElementById("footer-image").innerHTML = "<img src=\"" + this.images[Math.floor(Math.random() * this.images.length)].src + "\" />";
  }

};


footerImage.initialize();