Technically, to have been circumcised, King David would first need to have existed. However, even without existing, notional David could be described as having been circumcised. Presenting an image uncircumcised, as Michelangelo did, then ought to suffice to, er, sever any proprietary claim, as it cannot then be the same notional David, but another unspecified stand-in David, perhaps akin to the popularly blond and blue-eyed stand-in Jesus.

Jesus, by the way, is described in Paul as having been constructed, after the manner of Adam and of saved souls' post-resurrection bodies (even now awaiting them in heaven against the fore-ordained apocalypse), from aforesaid David's (implied captured and preserved, or allegorical) "seed". This too does not require actual existence. The waiting bodies, notional or manifest, canonically lack anything for foreskins to be attached to or severed from, perhaps a mercy, and presumably navels as well. No forecast is made about nose hair, either way. Jesus, in contrast, as a fertility totem is necessarily endowed. Who would essay to circumcise Him is an open question; theologically, He doesn't seem to need it.