[DH]

The images are uploaded via members albums, so my guess is, the person who uploaded that image has since deleted it from their album, which should have removed it from the group, but has for some reason left it :s

Or the member has been banned or pruned because of a low post count.

EDIT: I have removed the orphaned thumb image, obviously the database held onto the thumbnail, despite the image being deleted from the banned members profile. Anyway, it was not a problem with the vB update, it was more a problem with one of the members.