What good is a felt board (click here for directions) without felt board pieces?
To make pieces, either color copy pictures from books or use stickers.
Mount on felt or mount on thick paper and affix scratchy velcro to the back.
I'd prefer felt if it's going to be played with flat, but velcro if it's going to be used for travel or at an angle (think on a teacher's lap during circle).
Cost: Less than $0.50.