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 don’t picture them at all. If the author gives a descriptor multiple times then I generally keep that in my imagination because there must be a reason for stating it more than once. I’m part of the no visualization crew so I don’t really bother myself with details that aren’t given. Characters, to the extent that they exist in my mind, are made up of their actions, thoughts, and situations, very rarely are they given a face.