If anybody is still around to see this:
I'm only posting this here because it's been several months and this hasn't been resolved yet. Lately, the wiki has been having some problems with image thumbnails. The problem seems to have originated around the time the wiki came back up after being completely down fairly recently, so it doesn't affect images uploaded before that time unless a new version is uploaded or the size is changed on whatever article it's posted on.
While images will display at their native size just fine, attempting to include it as a thumbnail (either in an infobox, a gallery, or otherwise) results in an error. For certain cases I was able to use a workaround (setting the image size to 180px, the default size for thumbnails if the size is unspecified), but this isn't a proper solution by any means.
So if anybody is reading this and has the power to fix this because I don't, that would be a huge help.