var images = ["path/to/image", "path/to/image", ... , "path/to/image"],
    preloaded = images.length;
      
_.each(images, function(img) {
    var image = $('<img />').attr('src', img);
    image.on('load', function(){
          preloaded--;
          if (preloaded === 0){
              console.log("All preloaded!");
          }
    });
});