The Quick Info functionality can't show images :(.
E.g.: try to do a Ctrl+Q on JRootPane - the javadoc has two images but none is displayed.
(for JDK 1.5)
Or see the same with JLayeredPane, JScrollPane, or other API that has images in description
I recall however that I saw images in the QuickInfo window while working with IDEA 3 or earlier.
Thanks in advance,