Personally I give each character a face, either from a person I know who matches their personality or a celebrity that fits the description, even though sometimes it can be really annoying if the author gives more details on the persons appearance and my character doesn’t fit that lol. I’m very curious as to what other people do.
I usually picture a celeb or reality tv star. For example, The guest by Emma Cline… I pictured the narrator to be Raquel Leviss.