I wrote a fanfiction about it once, called "Quincey Morris' Letter".
My story basically picks off from the very point where Stoker's novel ends, with Quincey's death.
In my story, the ending is slightly altered; Before his death, Quincey gives Mina a letter, addressed to his fiancée in Texas.
The letter reveals Morris as a womanizer, who left his pregnant fiancée and escaped to London because he could not bear the responsibility of living with her. He continues his love affairs in London, having an affair with Lucy, but after her death and the discovery of Dracula, he remembers his family's curse and realizes God is punishing him through Dracula. He decides to return to Texas right after he defeats Dracula, but unfortunately, dies before he could do it.