Our vBulletin is indeed set to show this behavior.
Attachments and / from the personal albums are only shown to logged in users.
This way pictures which might contain personal / private / copyright protected content, won't "spill out" to the public by robots and data harvesters.
Additionally, it was thought that more people would join the Forum when they see more logged in.
Your embedded pictures can be seen by anybody who is logged in to the Forum.
I don't know what happened to your usual way to embed external pictures to your posts. I don't know of any change to the settings of the Forum.
The Forum Rules in the registration process might indeed be a just slightly (if at all) altered version of the default Forum Rules that come with the software we use. I'll see what we can do to get it changed and put up to date.
It probably will take some time, because not only Danielle is involved herein, FTVGirls also is, as they actually pay for the hosting of the site. They might want to double check any changes to be on the safe side.
Again, thank you for getting that to our attention - and welcome to the Forum!