I think I’ve fixed this. Before the site would force secure pages on everything, including images that weren’t originally hosted on a secured site. So, http would be forced to redirect to https, which apparently broke some images that were set to load via the insecure protocol. (and in turn failed to redirect)
Hopefully by removing this rule, images will work. Really wish Steam forced HTTPS though… but meh, Valve security is their concern, not ours.