Who painted the swimmer in somethings gotta give?

The painting of the swimmer in "Something's Gotta Give" is not a real painting, but rather a photograph taken by Annie Leibovitz. It is a famous photo of Diana Ross, and in the film, it's described as being a photo of a "famous athlete".

The filmmakers likely chose this photo for its iconic status and the way it captures a sense of motion and energy, which is fitting for the character of Harry, who is a successful film composer.