I couldn't find it but I made a quick one:
http://nuvisiongroup.com/test/cookietest.html
you should get a green image if you have cookies turned on, red if you don't.
http://nuvisiongroup.com/test/cookietest.txt - source for the html page
http://nuvisiongroup.com/test/image.phps - source for image.php
Doing it that way doesn't fit everybody. But it's a good way to do stealth cookie testing.