I wonder if putting art on inner PCB copper layers is more common? Similar to silicon art on ICs? It would only be visible on x-ray and to people in the PCB fab

I wonder if putting art on inner PCB copper layers is more common? Similar to silicon art on ICs? It would only be visible on x-ray and to people in the PCB fab. I've never personally done it, or seen any in the wild, but it seems more likely to get away with? On a commercial product, something silly on a silkscreen is quite likely to be noticed by someone without a sense of humor.