François Boucher [Public domain or Public domain], via Wikimedia Commons
I saw this at the Wallace Collection and was fortunate in that soon after I had seen it there was a Gallery talk by a member of the Wallace Collection staff on the painting, so I was able to listen to the talk.
What I found interesting about this painting was the way in which Mme Pompadour had used works of art and commissioned paintings to increase her influence at the court. I also discovered the symbolism contained within this painting and what Mme Pompadour hoped to achieve through it.
My notes on the painting are here: Madame de Pompadour