This is an easy way to pre-load images on your site: just add the images’ paths to the DIV class, and call the DIV in your HTML.
In other-words, you will need to inject the "loader div" somewhere in your html. You can even stick it in the footer of your site, if you don't have "injection points" at your disposal.
Just add this HTML:
...and add the following custom CSS (below). The DIV will not be visible but the images will preload nicely.