Fellows,
There isn't anything odd going on with the photos.
The forum is currently setup so that to see photos that are hosted on GT40s.com you MUST be logged in. There is a catch....
On some posts the images are not hosted on GT40s.com but linked in from somewhere else. Like this photo
- the 163 will appear if you are logged in and if you are not logged in. 
The photo below that I am placing in this post as an attachment should only show up if you are logged in. It will not show as a thumbnail unless you are logged in, it will show as a file name. If not logged in and you try to view it then you'll get an error that you do not have permission to view it: