gistfile1.js

var photos = ['Resources/P5240181.JPG','Resources/P5240182.JPG','Resources/P5240183.JPG'];
var FREQUENCY = 5; //seconds
photos.each(function(elm,idx){
  var path = elm.toString();
  photos[idx] = new Image(); //preload for faster transitions
  photos[idx].src = path;
});
var idx = 0;
new PeriodicalExecuter(function(){
  idx = (idx + 1 < photos.length) ? idx + 1 : 0;
  $(document.body).setStyle('background-image:url(' + photos[idx].src + ')');
},FREQUENCY);