your entire /images/ folder - no content specified
Do you mean that they're requesting /images/ like that? They're hoping to find an index file-- probably auto-generated-- that will helpfully provide a list of all images in one handy location. Do not oblige them. (This is generic advice for all image directories everywhere, unless you've got some specific reason to do otherwise.)
btw, those are all the same IP. Well, two IPs. 184.108.40.206/19 and 220.127.116.11/20
:: off to pursue line of thought ::
Nope, nobody's been snuffling around any /images/ directory lately. I tend to auto-ignore 403s, which is what they'd get, so I had to go back and check semi-manually.