Hi Cheyenne and Niall,
Yes, all wiki images seem to be corrupted in a strange way. Unfortunately, the only backup of these files that I have is in the backup of the wiki itself, since the images and other files are within the wiki directory tree. So I regret to say that we have no way to recover them. I have no idea what the cause is for such corruption.
The image on the front page can be easily replaced, but the figures in some tutorials are much harder to repeat. I am sorry for this problem; AFAIK, this is the only data loss we've had during the migration to the new server.
I'll try to fix this as well as I can, as soon as possible. Right now my maximum priority is 1.6, so I may be a little slow...