Hello Pierrick,
Me as a beginner in Blender started today and I am very happy with your tutorial, it’s my first time using sculpting in Blender and you do really a great job explaining. I had to stop for today, and I know that the neck is still missing. I will render a front view out, tweak the proportions in Photoshop. Then I will load the image as a plane in Blender to help me tweaking the proportions in 3D as well.
Thanks a lot, Pierrick. Here is my result so far:

Best regards, Peter