Audio problem: As soon as Nemo begins playing the record, we hear a woman say "Ready, professor?". However, the actual recording doesn't start until the needle is put into position, which is after she says that.
Continuity mistake: When the assassin takes Mina as hostage and holds a knife to her throat, Mina's scarf is under his arm. Two shots later the scarf is hanging over his hand. (00:27:50)
Dorian Gray: Ah, the bedroom. Does it give you memories or ideas?
Mina Harker: Ideas. [Stabs him in the lower parts.].
More trivia for The League of Extraordinary Gentlemen
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.