Please add previews for images

It’d be great if the plugin supported previews (empty blocks of image’s size would be enough) and fade-in effect like the a3 Lazy Load plugin does. I prefer the Speed Up plugin because it applies lazy load even background images and supports any custom attribute for no-lazy-load. If this plugin had some animations and kept image size before the image is loaded it would be the best plugin of all existing.

Thank you!