Ha! I know exactly which stock photo website Google was talking about! I just went to visit it and see if changes had been made. Several weeks ago, I visited the stock photo site, page one of the SERPs (PR7), looking for free stock photos, and I thought it was crossing the line. Its layout was almost visually identical to the layout example Google now says is banned. It had lots of small images about 60 x 60 pixels next to the Google text ads.
After reading Google's official clarification, and all preceding posts in this 100-post thread, I think the issue is: the misuse of small images as if they are individual hyperlink icons (like thumbnails).
Most site navigation uses text or icons or both. If both are used together, typically the icons are small images adjacent to the text, with the icon appearing to the left of the text. When both text and icons are used, and both are links, website visitors naturally assume or tend to think they are interchangeable, i.e., the text link to the right of an icon is intra-site navigation, not an ad, or a link to another (extra) site.
Do you remember when "images next to ads" was the "hot new thing" in Adsense? It seemed ridiculous at the time, but a lot of people bought into it.
I take it to be a clarification mostly about icons simulating navigation links. As in one image for one ad (1:1 ratio). The 1:1 scheme is so silly. Why would any webmaster do that unless it was to create the perception of a direct link between the image and the link, knowing full well it is common for small images next to text to be navigation icons.
If more clarification is needed, Google can simply give visual examples of other ad sizes and its position on them regarding what is misleading. I don't think that one large image with a skyscraper is going to cause the same confusion, because it has a link:image ratio of about 4:1.
Your site should have images and the images should have something to do with the content, and the ads are content-based. Just stay away from one image per link. I don't even think you have to worry about blending if you steer clear of small images in icon styles.