The background on the frame is painted in shades of metallic silver, and the leaves and flowers , being non metallic, stand out sharply. It is a nice effect.
Silver leaf in very, very thin sheets is applied to a sticky surface, sometimes I use the traditional terracotta ground, which seems to add to the depth and brilliance of the leaf.
After it has set a while, the excess leaf is gently brushed away, with a soft brush. Too much brushing or too harsh a brush can scratch the silver, even right through.