It is not Haraam , but not advisable for Muslim woman to do so especially if she is young.
If she displays her picture in public media with full Hijab, it will be the responsibility of Muslim men who know her, not to look at her picture.
Many Maraaji' of Taqleed say that it is not allowed for men to look at the photo of a woman whom they know even with Hijab.
Wassalam.