“To paint well, I need to be enraptured by my subjects,” the American artist Elizabeth Peyton said in 2009. It should come as no surprise, then, that she frequently paints portraits of fascinating people she’s never met—Napoleon Bonaparte, Serge Diaghilev, Frida Kahlo—along with well-known yet unknowable celebrities: Queen Elizabeth, for one. The National Portrait Gallery places more than 40 Peyton works among its historic portraits—for an energized interplay. —J.V.