The images in TDF wiki now have loading=“lazy” attribute thanks to this config option:
https://www.mediawiki.org/wiki/Manual:$wgNativeImageLazyLoading
This means that bandwidth will be saved, if you open a long page with big images and don’t scroll to the images.
People with slow connections might do some tests and let me know, if the browsing experience is OK (is the lazy loading annoying). Pages with lots of images can be found through here, for example:
https://wiki.documentfoundation.org/Design/VisualElements
Larger images in a long page:
https://wiki.documentfoundation.org/Marketing/Material
Web browsers optimise the moment of loading based on the connection speed:
“On faster connections the threshold is smaller. On 3G the threshold is 2500px and on 4G it is 1250px. This means that the browser will look 1250px below the current scroll position and will start loading images within that threshold.”
The feature is quite new in browsers, so I think it will be optimised further in the near future. It is not yet in a stable version of Safari: Lazy loading via attribute for images & iframes | Can I use... Support tables for HTML5, CSS3, etc