My suggestion: once you have your movie list, divide it by year so you can also see the development of film. Like you have the silent films, then there's a little spurt of musicals when sound becomes available, that kind of thing. You can also see how historical events are reflected in the movies, either by escaping or engaging in what's going on.
And even if no one recommends them here, throw in a few of the films that redefined film, genres or cinematography - if you watch a bunch of early movies first, you can really see how films like Metropolis or Citizen Cane affected the films that came after them, but you're only really going to notice it if you're watching your film list chronologically.
His first sound film. First film starring Peter Lorre.
Someone is murdering children, throwing the town upside down. The police begin cracking down on all criminal enterprises, and the criminals, working with the beggars, vow to catch the killer themselves.
Ikiru
Casablanca
The African Queen (edit: my memory sucks and this is not in black and white, but it's a good movie)
Night of the Living Dead
Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb
Though it was made in black and white as an artistic choice and not from the lack of availability of color film, I highly recommend Young Frankenstein.
The 39 Steps - my very favorite Hitchcock movie. I know, others will say they prefer North by Northwest or Rear Windows or even The Birds, but I just find The 39 Steps completely captivating and charming at the same time. It's an old war-time story of spycraft and adventure that still holds up, although the cultural reference are pretty stale at this point.
I think the 1951 adaptation of Dickens's A Christmas Carol starring Alastair Sim is worth a watch during the holidays. The original British release was titled "Scrooge" but it was released in the US as "A Christmas Carol" so keep that in mind if you go looking for it.