Found a broken animated image on http://raikissu.tumblr.com/post/175730802572/oh-my-gosh-i-have-that-exact-same-spyro-shirt
The problem seems to be that the image is not a regular gif, but a gifv. There's no check for that file type yet in the script.
Just adding it as an AND to the gif check should work.
if ((match !== ".gif") && (match !== ".gifv"))