I'd like to change the thumbnail selected by Photo.app for some of the people on the
Faces album, but I can't seem to find that option. Also, consolidating some of the suggested names –which I suppose are contacts in some of the cases– would be great.
Right-click on the
Facesalbum you'd like modify, and click
Double click the small round photo that appears on the fifth row of the info pop-up. All photos in that album will now appear behind this pop-up.
Right-click the photo you that you want to use as that Faces album thumbnail, and click
Make Key Photo.