A Sherlock Holmes theme would include e.g. a Moriarty figure, a Hound of the Baskervilles set, a crime scene set, some bobbies (which would be wildly popular), and other scenes from the stories that I don't know because I haven't read them.
And Mrs. Hudson! A Sherlock theme would basically be a mini, slightly darker, Victorian theme plus a big scary dog, police detectives (Lestrade and co.), and some science equipment. It could have a bridal couple, some aristocrats, Irene Adler with portrait, Sherlock in different disguises, a snake, a violin, a carriage, a handheld lantern, a pipe... Most of the famous stories are out of copyright, so the few lingering ones are not a huge concern.
Speaking of Doyle's work, his Lost World should be out of copyright as well. It's not as famous as Crichton's, but who doesn't love dinosaurs and Victorians?
I see no reason to go into licensing because there's already so much material in the public domain. Alice in Wonderland would be a pretty popular one. They have the queen already.
Since they are going into licensing, I would choose things like Peter Pan (it has a special copyright extension because Barrie willed it to a children's hospital) and le Petit Prince. Playmobil would do well to side with more "intellectual" themes.
