Or better yet an option to display the title/alt text of an arbitrary image.

from retroj: I would like to have a browser object class for alt text. This just raises the question, if
the alt attribute can be referred to as a browser object, what would be the accompanying
browser-object-command? Perhaps show? Since the browser-object commands are supposed to be high level and
generalized for different types of browser objects, show could also be used to unhide collapsed DOM node
browser objects.

Since a few weeks ago, you can use the key sequence `* a c' to achieve this effect.