bestonia

This is actually super easy to do with just a bit of css. Add the following to your theme file. In this case my loader gif was 32px by 32px big so I set the min height and width accordingly.
It does make a world of difference to show a small loader to people to let them know the page is loading vs just nothing..

img.lazy.loading {
	background-image: url(/some/path/to/your/gif/lazyloader.gif)!important;
	min-width: 32px!important;
	min-height: 32px!important;
	background-position: center!important;
        background-repeat: no-repeat!important;
}