The problem is the permissions, as far as I can tell. They appear to be 600 when they should be 644, since 600 and a few others close to it basically mean "the owner can do what he wants, but no one else can do anything."
And since when accessing an image it doesn't run that part as though it's the owner, it throws a 403 because the viewer doesn't have permission to read said file either. Make sure all the images in there have the read permission (or just set to 644 to start, and then start taking away permissions again) and see if that fixes it.