Calico Pie's Family Historian software allows the user to add photos and link faces in the photos to their entries in FH. The feature list says:
In Family Historian, not only can you add as many pictures as you like for each person, you can add a picture once and link it to each
person in the picture. The best family photographs are usually the
ones which have more than one family member in them. In Family
Historian, you can link each person to their own face in each picture
they’re in – without having to ‘crop’ your pictures. By using Family
Historian in this way you add value to your pictures by recording who
each person is, while at the same time adding value to your family
tree research by making it much more visual. You can display pictures
(and faces from pictures) in diagrams and reports, and family tree CDs
& DVDs, and websites. Family Historian will by default use up to 9
pictures of each individual in the main program window.
You can also add sounds, video and any other kind of multimedia. You
can even add links to other family tree files.
Screenshots of the feature are on FH's tour page, in the Pictures and Multimedia section, and as part of the Quick Start Guide.
Calico Pie's You Tube channel has a tutorial that was posted using an older version: Adding Pictures and Linking Faces (in Family Historian 5).
A 30-day free trial is available. The trial is fully functional except for a few features like plugins.
Disclaimer: I am not associated with Calico Pie. I am a long-time user of Family Historian and a member of the FH Users Group -- for more information, see FHUG's Forum and Knowledge Base.