Dear Judith Meijer,

There is two widely used datasets for human faces: 

1. ORL (Olivetti ResearchLaboratory)

2. Yale face recognition

You can find in this link all the face human datasets:

http://www.face-rec.org/databases/

Best regards,

S. A. Medjahed

Urszula M. Marcinkowska of Jagiellonian University, Kraków has expertise in Evolutionary Biology and has been doing some work with faces.  Her work may be a good starting point for accessing databases.

Hope it helps!

The Chicago Face Database has many male and female faces to select from and, from my perspective, do demonstrate variation in their masculinity and feminitity. The database was not designed for that purpose, but you might consider selecting some subjectively and piloting the images with participants rating these faces on your variables of interest.