gistfile1.js

start = function() {
  all my framer code
}

preloadImages = ["a.png", "b.png"];
preloadImagesCount = 0; // How many images were loaded

preloadImages.map(function(image) {
  var imageLayer = new Layer({image:image})
  imageLayer.on("load", function() {
    preloadImagesCount++; // Add one to loaded images
    if (preloadImagesCount == preloadImages.length) {
      // Run Framer code if all are loaded
      start();
    }
  })
})