Checkout how FF renders a standard domain validated cert on a site versus one with extended green bar validation:
https://www.expeditedssl.com/assets/browser-ssl/thumbs/stand...
https://www.expeditedssl.com/assets/browser-ssl/thumbs/exten...
The gray icon might as well not be there as far as consumers are concerned and blue vs green crossing guard icons really fail to indicate anything of use to an end user.
If you want to see a big list of SSL UI screenshots, I have them up at:
https://www.expeditedssl.com/pages/visual-security-browser-s...
