Google AdSense has recently added a couple of new ad unit styles for regular publishers, although neither of them can be controlled by the publisher. First, AdSense is testing an unbranded ad unit where they have removed all Google branding from the ad unit, which virtually makes it impossible to identify the ad unit as advertising.
The second is a style that has been tested for a month or so, although new variations of it are popping up. In the ad unit, which is showing up in multiple ad unit sizes, one of the ads within the unit is replaced with a relevant image. Then the image links to an Ad Links results page. The newer variation of this has "See more sponsored links > >" underneath the image.
Publishers are unable to control if or when these ad unit styles appear on their sites. The unbranded ad unit does not seem to be used very often at all, however the image within the ad unit style is showing up frequently on many publisher sites.
It is always interesting to see what AdSense is testing, and what eventually makes its way to being a regular part of the program instead of limited testing.