> > > The problem is that image files are being saved locally 
> > > as .html files.
> 
> What HTTrack version are you using?
Version 3.33. Thank you for asking (I'd intended to include ver in my original
post, and then forgot).

This is the first time I've ever got this symptom, and I've been a heavy user
of Httrack for several years. Now, it is also the first time I've seen URLs
quite in a format like these, of some dynamism mystery wiki deal behind the
scenes, that which is beyond me.

Barren of strategy, I've experimented toggling the few settings I could think
of (such as old Http head requests, or explicitly declaring the implicitly
defined mime types), but to no avail -- and am totally out of ideas on what to
try. 

All the binaries (I later noticed it had some zips, in addition to images)
from that wiki site persist in being saved to disk with *.html filenames.