Just tried it. It tries to load, then goes back to the translation boxes and tag 'list'.
Edit: It /seems/ to just be that pool, and may only be select images in it (I tried a few others and they were having the same problem). Normal images and other pools - so far - seem to be loading fine.
I believe that's what FF does when it sees images with errors. Have you tried opening just the image URL in a separate tab? Does it say "image 123467890.jpg can't be loaded because it contains errors"? If so, please include URLs to posts where it happens.
Yeah, the image itself works just fine. Tried refreshing (and ctrl-F5, which I've heard does a more... thorough? refreshing) on the Danbooru page and it still won't load up there, though.
Edit: It seems to have fixed itself somehow. Just noticed that. Gonna check the other images to make sure they work.
Edit2: Right, now it's just getting /weird/. I decided to check the image after that one, to see if it was broken too. It was. So I went back. The 'other' image is now fixed. But it only worked for that image. The others throughout the pool still load the tag list.
I sometimes have a similar problem as well (Images don't load, but the notes do), and I usually resolve it by closing my browser and clearing my Internet cache.
I also have NoScript running, and google-analytics is blocked.
It may not actually be Firefox; I've seen similar problems sometimes when an ISP is running a transparent proxy (which basically all of them are) and has the caching set too aggressively. A good test for this is to open the page in a different browser (but on the same computer); if the same problem shows up there, it's probably your ISP.
Force-refreshing the page will usually cure this. (In Firefox, I use Shift and the toolbar Refresh button; I've found Ctrl-F5 to be less effective, but that might just be me, and it may depend on your ISP's cache as well.) You might need to open the image directly first, though.
(This can also happen if one of the two Danbooru servers is playing up, but as far as I know they've both been fine for a while; they certainly both work right now.)