GR translation: white stock

[Mike Jing]

V568.28-33, P578.21-26   The crowd next morning is sparse and placid: old
people and children, and a few silent veterans. The Viking invaders are all
kids, helmets sloping down over their eyes, capes dragging the ground,
shields as big as they are and weaponry twice as high. Giant Plechazunga
images with white stock and red and blue cornflowers woven onto the
wiremesh frames, line the square.

What does "stock" mean here?