I just visited the SE logout page and it seems that the stackapps icon is missing:
This doesn't seem to affect site specific logout pages:
This seems to be because the site specific logout pages uses this image:
but the network wide logout page uses this http://cdn.sstatic.net/mathoverflow/img/favicon.ico
And stackapps uses some other URL that wasn't updated.
It doesn't load: http://stackexchange.com/content/stackapps/img/favicon.ico
It should actually update and use this: http://cdn.sstatic.net/stackapps/img/favicon.ico