I don't know if Facebook made any changes to its site or how photos are loaded.
That's one possibility.
The other is that your software for your Nook Color updated.
What happens when you download the free Dolphin Browser App and go to facebook with it?
The photos show up indolphin. But comments on my page do not. Dolphin is confusing to me.
I'm not aware if there are any other browsers available.
Have you tried the mobile version of the facebook site? It should be something like m.facebook.com. or facebook.com/mobile.
does that work?
Facebook made some sort of update last week that appears to be affecting the Nook. Haven't tried pictures but I'm unable to comment or see more than a few entries on my newsfeed because of it. Haven't heard anything about a fix.