Someone was actually doing a series of paintings of herself having sex with all of the Presidents of the US (in order) earlier this year, I think...here we go, Justine Lai. NSFW, naturally.

Still, I don't know if it's the same thing. There are certainly more issues than race involved (I'd argue that the nature of celebrity today affects both the likelihood of naked paintings and the inclusion of the First Lady) but I'm hesitant to conclude that race is not a factor.