gistfile1.js

$("#profileGallery .vehiclePictures").fancybox({
  'onStart': function(arr, index){
    if(arr.length == index+1){
      // ajax call
      // update #profileGallery with the last image from the previous image batch + images of next batch
      $.fancybox.close(); // hide current Fancybox
      $("#profileGallery .vehiclePictures:first").click() // click on the "first" image (also the last image from the previous batch)
    }
  }
});