> Ok, so I did a bit of searching and found this:
> 
> 'User-Defined Structure'
> with something like: %r/%h%p/%n%[id:-:::].%t

I don't understand that either, but I think the post would create a mirror in
the form:
html1.htm
html2.htm ...
[jpg]jpg1.jpg
[jpg]jpg2.jpg
where the jpgs are shared among the htmls

If I understand you, you want a mirror in the form:
[dir1]html1.htm
[dir1]jpg1.jpg
[dir1]jpg2.jpg
[dir2]html2.htm
[dir2]jpg1.jpg
[dir2]jpg2.jpg

for that I would suggest using httrack in a loop
for /l %A in (1,1,999) do httrack site/%A -o dir%A ...