I'll pull some out of my *** - I mean, 'back pocket' - and go with gut feelings on who I remember.
Unfortunately since it's HPL we're talking about here, that means white men get almost every spot on this list.
Harvey Walters - like others have mentioned, seems to be the prototypical HPL old man scholar here. Plus he's in virtually every version of Call of Cthulhu since they invented the game.
Norman Withers - old scholar again.
Diana Stanley - she wouldn't have been written about, but if you look closely you could imagine her in the background or between the lines of an HPL story.
George Barnaby - mainly because he's an old white man, learned, and is rich enough to travel (he even has a boat in his picture).
Leo Anderson - did he become a background explorer in the Mountains of Madness?
Luke Robinson - can see him in the vein of Erich Zann or hanging in the House in the Mists.
Monterey Jack - MAYBE
Roland Banks - with the gang clearing out Innsmouth.
Silas Marsh - on the boat to R'lyeh
Vincent Lee - medical doctors seem natural.
any female researcher, scholar, secretary, etc: I'd like to think so but not typically HPL.