The Stack Exchange global inbox (at the top left of the title bar) doesn't have a no-image alternative.
Browsing the normal (non-mobile) site with images turned off on a slow connection, the link still works, but there is no text to tell you the link is there. If you have pending inbox messages the number in a red circle does show up.
I'm seeing this with Opera 11.50, on Windows 7.
Just to clarify the Stackexchange logo link image is missing, but the link still works. The stackexchange alt-text on the popup is present