If you follow the Adsense TOS you shouldnt have any problems at all.
But anyway, recently I made a change in my ad display that involved an image, I wasn't quite sure if it followed the TOS correctly so I decided to go to the source. I contacted AdSense support asking about this and provided them with an url where they could see an example of what I was talking about.
They replied to me rather fast and they were very polite, they told me that they appreciated that I took the time to ask them and told me that there was not problem at all.
I think your best chance, and what I recommend, is to make and example page of what you want to do and contact them.
Recently, I saw a 728x90 adsense ad on a site. Above this ad, there was 4 thumbs size pictures of some celebrities without any embeded link in the pictures. It was simply creating the impression that to see those images one should click on the any of text ads (728x90 usually display 4 ads - and this pictures was perfectly above these 4 blocks).
My first impression to this practice was that it was a violation of ToS, but I am not sure....