You may also want to read

Nonviolent Action Method #8: Banners, Posters, Displayed Communications

From Gene Sharp

The Women of Liberia Mass Action for Peace was a movement of thousands of women who, among other efforts, bravely took to the streets united under a banner that said, “The women of Liberia want peace now.” The movement’s organizer, Leymah Gbowee said, “It was the first time in the history of Liberia that Muslim women and Christian women came together.”

(You can read more about the different methods of nonviolent protest in Gene Sharp’s book The Politics of Nonviolent Action.