Playing Miss Marple might be a bit of a challenge but definitely doable! I love having a couple older adventurer or sleuth types in games like this. She can keep the younger members in their place. haha.

I'll wait to see what other types people want to play before I narrow down my choices, but I'll have and older distinguished male and a younger ambitious female to round things out either way. : )

Edit:

Here's a short list of some characters if you're stuck on ideas.

Male=
Dorian Gray
Dracula 
Jonathan Harker
Dr. Jekyll/Mr. Hyde
Victor Frankenstein
Erik (Phantom of the Opera)
Sherlock Holmes
John Watson
Jay Gatsby
Huckleberry Finn
Robinson Crusoe
Ichabod Crane
Atticus Finch
Jean Valjean
The Invisible Man

Female=
Mina Murray
Christine (Phantom of the Opera)
Jane Eyre
Irene Adler
Scarlett O’Hara
Lizzie Bennett
Nancy Drew 
Anne Shirley
Jo March

As long as the character comes from classic literature that can be adapted to the 1940's will work.