Google is seeking new revenue sources, as growth slows down for the four-line text ads that generate the majority of its sales. Its revenue increased 56 percent in 2007 to $16.6 billion, less than the 73-percent growth in 2006, Bloomberg reported.

“We haven't found a proper way to monetize image search to date,” said Mayer. “You may see us roll out an ads-image search in the future, but when we do you'll know that's because we found a way that ultimately enhances user happiness with the product.”

Google estimated that in 2006 it was giving up about $200 million a year by not including text ads with its image search results, which has probably increased since. Trials showed that text ads drove people away from conducting image searches, and Google dropped that idea, according to Bloomberg.

Mayer said that display ads may work better with image searches because they seem more natural to people looking for pictures. The company has done mock-ups of how it might present the ads, but has not yet tested them on users.