$(document).ready(function() {
  var randomImages = ['inside1','inside2','inside3','inside4'];
  var rndNum = Math.floor(Math.random() * randomImages.length);
  $("#inside #callout-container").css({ background: "url(http://www.newattitudesalondayspa.com/wp-content/themes/nas2011/images/" + randomImages[rndNum] + ".jpg) top center no-repeat" });
});