I would use metal for the cover, probably aluminum. There are lots of interesting and elegant ways that you can decorate aluminum. There's acid etching, like 40hz described, laser etching, waterjet cutting (for intricate grillwork), and all kinds of architectural finishes. You've seen James Trussart's instruments, right? The metal cover will be durable and light weight, and conductive if you want it to provide shielding too. If you want to use one of those laser cut wood pieces, I would epoxy it onto an aluminum plate, for the same reasons.