A bit of a "nerdy" question -

But what determines whether a user’s picture appears in that column of the forum front page? For instance -

Only two of these have pictures, but while other users have created one - as evidenced by posted observations - they don’t appear here.
No significance, just wondering…

Original or Frequent or Most Recent is revealed if you ‘mouse’ over the Icon.

The forums aren’t integrated with the rest of iSpot, so I’d guess that you have to set up pictures separately for both.

Yes, I remember doing that (Own Profile/Preferences)
There are a lot of things about the Forum that are mysterious!
I just found this illustrated analysis (at the Start of every Thread)