I suspect your biggest problem is that you’re using the full sized images. Some cameras create a separate thumbnail file “.thm” next to the image which you can use, otherwise you may want to consider making your own thumbnails or even using a custom canvas.
I am sure that there are similar functions on Windows, on the Mac you can use API to ask for a thumbnail from an image file, if it contains one, it will return that one to you, or it can generate you a thumbnail. Which is a lot quicker than loading the full resolution image and drawing it down into a smaller version.
It’s possible with some JavaScript and a thread, you could display the page and then create the thumbnails on the fly and update each element with the thumbnail your code created, I would suggest caching these thumbnails, maybe use the “.thm” file so it’s compatible with other applications also.