Looking at our gallery -> http://gallery.xpowerforums.com/
You can see that some categories do not have thumbnails down the left.
Some categories contain only categories, i.e. no images directly in that category - in that case, its understandable why they don't appear - although it should be smart enough to pick an image from the subcats in that case.
However, in the case of 'XPF Area Meets' - there is a photo within that category, but there is not category thumbnail on the home page.
Have we missed something?