Try Adding Images to Mobile Content Network
Advertisers looking to build brand have a new option. Google now serves mobile image ads on its mobile content network. As with the rest of Google AdWords, pricing is auction-based and you can set a budget.
If you’re planning a branding campaign, and you’re already using AdWords, why not try a test? You might get a good price, since I doubt mobile AdWords is as competitive as regular AdWords.
Only one image ad will appear per mobile page, according to the Google Mobile Blog. That gives you dominance on mobile sites advertising only through AdSense.