They look life fondant pearls to me.
I think the bigger ones are fondant pearls and the little ones are the pearl colored dragees (sp?)
I was thinking on the same lines as you coco - I have every color of dragees and non pareils known to man - does anyone know if you can "pearl" the white dragees or white pareils? And then how would you make them stick to the cake like they are in this picture? (the cake will be buttercream)
They look like edible pearls. The Bakers Kitchen has them in sizes from 4mm to 8mm. That's what I'd do...
Try clear piping gel spread thin on the areas where you want the pearls heavily concentrated and then just drop them on. Hand pipe dots for the bigger draggees that cascade down the sides.