A spinning icon (that you preloaded the second you opened the site because we use those icons everywhere) has absolutely fuckall to with the speed at which images are downloaded. The images aren't rendered before they've completely finished downloading because otherwise the double page option wouldn't work as intended. For single and long, I could technically change that, but it wouldn't actually speed up the download in any way. You'd just get blurry half-finished images to look at for a second.