With my browser (Firefox) I haven't found anything better than clicking on the picture to see it and using my Back key to go back to the thread, click on the next photo, etc. Often times there is a way to tab or otherwise move between pictures but I haven't found one yet.
A lot of forums don't support pictures because of misuse, band width, all sorts of reasons, but we sort of need them for quilting!
I actually rather like the thumbnail presentation, can click on them if I want or not.