The explanation of the cover design for Storyteller is on the back cover, but of course people looking at it online don't usually see that. Here is the relevent quote:
“Na, there will always be need for Bards,” said Kyan. “If not to sing the warriors’ deeds now, then to remember those who fought before, and teach those who will fight afterwards the way of it … We are like the pin in the cloak-clasp, the smallest, plainest part, and yet without it the brooch falls away and is lost, and the cloak with it, and the man perishes from the cold. So is it with us. If the Bards should ever take the Druids’ road west, it would be a black day for the Cymry, for what is there to hold a people together who do not remember their past?”
Make more sense now?