I got served in an ad unit along with text ads, a little picture in the place of one of the ads?!! it was in the leaderboard unit. so there were 2 or three text ads and one small pic ad - strange!
Yeah, I saw that the other day as well. Guess Google figured out that CTR is higher with a pic next to it, so they're doing it themselves.
I think those add format are up for a while now we just dont see it very often, might want to read the link below for more info about the image... http://www.jensense.com/archives/2006/06/new_adsense_ver.html