dlloyd:
It's just a tad difficult to "get the big picture" as we sometimes have to scroll through an image at a molecular level. An option to deselect or choose image auto-scaling could be easily be added.
Bandaid fix: I'm using firefox. Don't know how other browsers might behave. I click the thumbnail and get the REALLY BIIIG picture. I right-click on that, and select view image. It displays in a 'fit to window' mode, with a '+' mouse pointer that zooms in if necessary.
Hey anything is better than a thumbnail that -is- the full size image. 
Yes this forum software does things that I've never seen any other forum software do, but I get what I pay for so I'm not disappointed or excessively annoyed.