Maybe you can use two materials:
-One for the stones, can be a stacked stones texture or a stonewall cladding. Just normal material with displacement.
-The other can be a material with alpha for the cage wires, or you can model these with a spline turned in to geometry.
This way you can control the size of the wires, the type of the stones inside. And you'll also have the shadows of the wires hitting the stones.