Cryptographic equivalent of family coat of arms
You can put almost any information in an X.509 certificate, and then pass the private key for the matching certificate along. People can of course claim that the certificate is theirs, but when holding the private key, you can prove it belongs to you.

Of course, you might need a central authority for the certificate to be trusted, but you can send a certificate request to many CA's. Of course, if there is sufficiently weird info in there to be notified you may need to explain the applicability (and most likely, pay up, but I guess that comes with the domain). If you start to dislike the CA you can always switch to another one.

Probably easiest is to include an URL to a website with e.g. an actual coat of arms.



Digital information is usually not used to show off. If you require something more physical then you could get e.g. a gold leafed ePassport. For that you would probably need a high up person in the government (and be a complete and utter - well you can fill that one in yourself).