I don’t think that’s actually an issue. A thread of nothing but inline images works fine with Discourse. There are a lot of bare links in the screenshots thread (possibly issues with converting posts to the new board), but some images are embedded too, so I tested it.
The continuous scrolling does loading on demand, and the images will only load as far as you scroll. Were you to scroll far enough on an image heavy thread, the images you have scrolled way past will unload, and you will see them load again if you scroll back to where you started from. This is true even if you don’t use the blue scroll bar to jump around, just letting the normal scroll bar grow very long as additional posts keep getting loaded, and then pulling it back where you started.