They're down for me, too, as well as everyone on fanfiction. I've checked every computer I personally own, went to my local library and tested it on their computers, and even hopped on a friend's computer to see why the images aren't loading. I've cleared my internet cache and everything, but the story covers are STILL down. So, if I had to guess, it's most likely the server and notifying the admin would be the smart thing to do.