See here under 'encouraging clicks': https://www.google.com/adsense/support/as/bin/answer.py?answ...
Nor is this a new idea. Google addressed this issue back in 2007, and specifically warned publishers not to post images next to ads. I know because I was one of them. Here is a snapshot of my earnings from a site I ran back in 2007. Note the big drop in CTR around Feb 7th.
In my defense I was a brash 18 y/o at the time, this was a hobby, and I wasn't thinking long term. And ofcourse I did remove the images after Google clarified their TOS.
But at some level, even then, I knew that what I was doing was morally wrong. Technical loophole not withstanding.