After Klara catches Ganin searching Alyorov’s room for signs of Mary, they return to Klara’s room where hangs a copy of The Isle of the Dead, painted by the Swiss symbolist Arnold Böcklin; Böcklin painted several versions of the popular image between 1880 and 1886. Here is one version:
Perhaps a visual analogue to Nabokov’s many islands and kingdoms (by the sea), all associated with temporality and mortality?