We need to choose a CAPTCHA image.
To clarify, what we're looking for is an amusing picture to go on the CAPTCHA page...along with the CAPTCHA. The image will just be for added comedic effect; it won't be the CAPTCHA itself (the CAPTCHA is from reCAPTCHA). Check out the "HELLO FELLOW ROBOT" image on the current captcha page: photo.stackexchange.com/captcha
I'm not entirely sure what would demonstrate the idea of a CAPTCHA well, however I recently took an image that I called "Contemplation" that might fit the bill.
It would be interesting if we could find an image that visually demonstrated the idea of a CAPTCHA. Hopefully someone has a much better image than mine, as it is rather obscure:
[Copyright © 2010 Jon Rista]