On the old forum software, I always used the desktop version on my phone (because the mobile version was terrible).
With the new software, the mobile and desktop versions appear to be exactly the same (which has its own nuisances, like not being able to see signatures unless you’re in landscape mode).
Anyways, there must be some difference between the mobile and desktop versions of the site, because switching between the two fixes the photos not showing up.
Here’s the mobile version of site (note the “Request Desktop Website” browser option):
And here’s the desktop version: