I find that the optimal solution is to load all images 'above the fold' (perhaps optimizing for a 'tall' screen) and lazy-load the rest, when they get close to

I find that the optimal solution is to load all images 'above the fold' (perhaps optimizing for a 'tall' screen) and lazy-load the rest, when they get close to being on-screen. if possible I also try to make sure loading these images doesn't change the flow of the page, but in most cases images have to fit/cover fixed dimensions anyways.