Could they be mounted inside a bowl rather than a plate, set
back below the rim? Unless you look down in the bowl it's
just a bowl. Adds a surprise factor - or an exclusivity
factor (I own it and know what's inside. You probably will
never see anything but a wooden bowl. If the metal is dark
maybe contrasting maple - with some chatoyancy inside and
out - the latter being nature's version of a hologram as a
visually semi-dynamic background. Shadows could add another
layer to the depth of the piece.

charlie b