Google announced an update to AdSense link units today. In select countries and site verticals, when users click on a link unit keyword, the resulting page will show thumbnail previews of advertisers’ landing pages.
Instead of a list of ads, here is an example from Google showing what the new page of ads looks like:
Google says their testing showed better click-through rates with the thumbnail images. The update to the new ad previews will automatically occur for publishers using link units in the affected countries and site verticals.