The pictures are copyrighted, so I won’t copy any of them here, but there are several more illusions by Akiyoshi Kitaoka at his website. For a really striking contrast effect, scroll down to the “Green and Blue Spirals” image.
UPDATE: And here is the page of illusions by Beau Lotto at UCL. Thanks to Jamie Dreier for the link. Again the images are copyrighted, so I won’t cut and paste any, but they are utterly remarkable. (Note that one of them is a brown/orange ‘illusion’ that, as Daniel Nolan noted in the previous comment thread, we might want to think twice about saying is illusory.)