There may other sources for Captain Nemo miniatures, and I would sure appreciate a mention of these. Please feel free to leave a comment.
Extraordinary Personages (captain Nemo (Prince Dekker) and Mr. Griffin)
Brigade games offers set of miniatures that include a Captain Nemo character. The characterization and impetus seems to come from The League of Extraordinary Gentlemen, a graphic novel, by Alan Moore and illustrated by Kevin O'Neill. I believe these are 28mm miniatures.
Reaper Miniatures also offers a Captain Nemo miniature. The inspiration for this 25mm miniature seems to be the British actor James Mason, which played Captain Nemo in Disney’s Twenty Thousand League’s under the Sea.