This question comes about as my really enjoying The Thing, finding out it had an earlier version, and then finding i enjoyed that version more and for different reasons.
Heresy!
Now I have that off my chest...
I’d love to branch out and watch more monochrome movies with modem ties.
The Fly - I have a boxset of all the various Fly films.
I Am Legend adaptations - The Last Man on Earth (B&W), Omega Man, and I Am Legend (as well as it's mockbuster I Am Omega). The novel inspiring:
Night of the Living Dead - as it's public domain anyone can remake it and they have (few of which are worth watching). A more interesting remake is the Dawn of the Dead one, although the original is in colour.
Nosferatu and Nosferatu the Vampyre but I'd also throw in Shadow of the Vampire about the making of Nosferatu.
The Blob - although the original was in colour.
And any number of Dracula, Frankenstein, Wolfman films.