The loading attribute is more interesting and useful but I think it's already fairly familiar to Smashing Magazine readers. I think the decoding attribute could be useful for page rendering on very low-end devices, maybe also on pages with a very large quantity of images.
This is an interesting one, although I find native lazy-loading with the "loading"-attribute more interesting: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/im...