The ads in question seem to be happening in the narrow skyscraper ad unit (120×600) and consist of normal text ads with a 90×110 image at the top (as pictured – image source).
I’m yet to see the ads live so am not sure whether the image is an actual ad or whether they are just an attention grabber (from the screen captures they seem to be just images/attention grabbers).
IF they are just attention grabbers then I’m a little confused as previously AdSense have asked publishers to ensure that images near ads be separated from the ads with a border but now they seem to be testing putting images in ad units – and images that don’t really have any relevance to the ad itself from what I can see.
Read about these new ad formats that AdSense seem to be testing at:
Update – it seems that these ads are also appearing in 120 x 240 ad units also.
Publishers are also telling me that the images do link to something but that they do not know what (as they are too nervous to click them as they are their own ads and don’t want to get in trouble).
Update 2 – I’ve just heard from another publisher that the images link to a separate page with a list of AdSense keywords on it. I’m not sure what this means exactly but am interested to see these ads in action.
Update 3 – Jen says these beta ad units are called vertical images and that the image acts similarly to ‘link unit’ ads.