It appears that photo images in Known standalone installs are disappearing somewhere in the hundreds of photos ranges. Two examples have been found by paging back through the photo content view.
E.g. this photo post and older ones are missing their images.
Example 2: @benwerd’s own site, werd.io, shows photos backwards through offset=420, however if you click "Older" there, you will see at offset=440 (or perhaps the next one) that one or more photo posts are missing their images, and are falling back to rendering only their alt text.
E.g. this photo post is missing its image.