Google's expanding the image ad formats available on Google Images by testing rich media leaderboard units that appear above Google Images search results and invite you to try new products and services. The new ad format is the old-style leaderboard display ad. The leaderboard is an image ad 728 pixels wide by 90 pixels tall.
Display ads on Google Images work the same as they would on other sites in the Google Display Network. It's easy to start running display ads on Google Images. Just use the AdWords placement targeting tool to target Google Images like any other site on the Google Display Network, and choose the type of content you want to advertise alongside.
You can upload your own leaderboard format ad or create one using Display Ad Builder. Pricing can be either CPM or CPC, depending on your goals.
More Info: Help Center