$(document).ready(function() {
  var randomImages = ['i1','i2','i3'];
  var rndNum = Math.floor(Math.random() * randomImages.length);
  $("#inside #callout").css({ background: "url(http://www.newlifestylefitness.com/wp-content/themes/nlf2011/images/" + randomImages[rndNum] + ".jpg) top center no-repeat" });
});