That's fabulously weird. My code is identical to yours, except the var cx = ' ' is different, of course. But if I run them side by side, mine has the icon and yours doesn't. Perhaps, while generating the code, you chose some option not to have the image? That's all I can think of.
Anyhow, I just went to the custom search page, typed in a domain name and grabbed the code. Maybe you should start again?