Drawing from old Hollywood publicity photos (I'm talking 30s & 40s old) from the Big Studios is always a great exercise, largely because the gorgeous black & white photography was so beautifully lit, so well crafted, that each image is a like a seminar in how to define the human form with lighting. The great photo portrait artists of the day like George Hurrell & Clarence Sinclair Bull created libraries of exquisite depictions of the royalty of old Hollywood that are admired and emulated still, and they're always fun to work from. Above is a drawing from a studio portrait of the character actor Edward Arnold (who frequently played evil industrialists in movies like Meet John Doe)
But with the various methods of streaming movie and TV content on computers and tablets (Watch TCM, HBO GO, Netflix, Amazon Prime, etc.) it makes it incredibly easy to draw from screen grabs from all sorts of programs, old and new. The thing I like about drawing from screen grabs is that you get to draw from equally well-lit shots of the Stars - usually with more expressions than just their glamour pose faces - but also you get to see the faces of the character actors and extras, also well lit and also with interesting faces and expressions.
The guy above is a good example - I have no idea what the actor's name is, but he played a bit part as a forlorn coachman sitting outside in the rain waiting for Greta Garbo in one of her silent films The Mysterious Lady. Random shot, but still a great face to draw, with strong lighting and expression.
Here's another character actor, named Frederick Worlock, from a Clark Gable/Joan Crawford movie called Strange Cargo - this actor shows up in a number of movies from the 30s, and has a fairly memorable face and presence - because I've watched it overandoverandover again, I recognized him from The Sea Hawk.
You can obviously draw the stars too - here's a sketch of Clark Gable emoting, probably from Dancing Lady, another Joan Crawford vehicle.
And again, from one of Joan Crawford's 30s dramas, a too-quick sketch of her that doesn't do her justice but is still a decent study I think.