I could be wrong but Google is not coming on the site and looking at any pics. What they are doing in monitoring the links to the pictures. So if you take a hot chick in a bikini from a church site and the same pic from a porn site Google will only have a problem with the one from the questionable site. Of course when you google images a lot of them come from more risque sites even if the picture themselves are n't that bad.
So I would believe just regular pics of cheerleaders, actresses and the works would be fine no matter how scantily clothed they are.
Of course I do not know any of this for sure but it is the only thing that makes sense. My site was flagged and shut down for a time because of the Kyla Cole pictures even though she was wearing a bikini.