Answer: After Quartermain is buried, we see a witch doctor performing magic above his grave and the clouds darken indicating something is about to take place. The witch doctor is chanting "Return" and the grave begins to shake. Although we do not see Quartermain come back to life it is most definitely hinted that he did and left room for a sequel which never came to pass.
Question: I've just watched this movie, but I'm a bit puzzled by what happens with Dorian Grey...what's the thing with the painting and why does he decompose at the end? I'm not up on the novels these characters come from.
Answer: In The Picture of Dorian Gray, Dorian has a painting that reflects himself. But while the painting grows older, Dorian remains young - the opposite of real life. In the movie, another benefit of this was that Dorian remained impervious to harm while the painting was preserved. When he finally looks at it, the pattern reverses and his body finally reflects the reality depicted by the painting, causing him to age past his own death very quickly. The other characters are from Dracula (Mina Harker), King Solomon's Mines (Allan Quatermain), The Invisible Man (Skinner, in concept if not in person), 20,000 Leagues Under the Sea (Captain Nemo), The Adventures of Tom Sawyer (Tom Sawyer), and The Strange Case of Dr. Jekyll and Mr. Hyde (Jekyll/Hyde). Some other characters also reflect classic literature, but these are the primaries.
Question: Do the creators ever plan on making a sequel? The ending is such a good cliff-hanger that I assumed it would return, although it has been over six years since the film's release that it looks doubtful.
Answer: The film was critically panned and a commercial failure. While the possibility of a franchise would obviously have been considered, the poor box office returns would have put paid to any studio interest in a sequel.
Question: I know that some aspects of the movie were altered from the source materials because of copyright issues and various other reasons (i.e. having Skinner as the Invisible Man instead of Griffith.) Were there any such reasons given for changing the nature of Dorian's portrait from Wilde's novel, or was that just altered to make his death scene more "dramatic?"
Answer: I haven't read this book of Wilde, but I think alterations were prompted not by copyright issues but because this conveniences the "league" storyline.
Answer: Allan Quatermain appeared in 14 books by H. Ryder Haggard, starting with 'King Solomon's Mines' in 1885, and ending with 'Allan and the Ice Gods', published in 1927 (two years after the author died). See http://www.fantasticfiction.co.uk/authors/H_Rider_Haggard.htm and http://www.kirjasto.sci.fi/haggard.htm.