I don’t know. I have the face in my mind but can’t find them. I mostly go with readers choice and write on their fandom.
I usually fancast people as actors I either fit the personality or the looks. I try to look for lesser-known actors, though. It seems like almost every black female protagonist is Amandla Stenberg nowadays.
In Marie’s Life, I cast some celebrities who are well known for kids shows, family shows, musicals and English dubs of Animes. For example, I cast Blake Shepard as Laito Sakamaki from Diabolik Lovers, John Partridge as the Rum Tum Tugger from Cats, Stephanie Sheh as The waitress A.K.A Usagi From Sailor Moon and Linda Larkin as Mrs. Jasmine From Aladdin. These are well-known celebs from all kinds of media.
I cast people I imagine in my head would be a good fit for the role.