Unlike professional licenses though, martial arts certificates are a private matter. They are for the recipient alone. They have no meaning outside the style or organization they were awarded in, and so there is no purpose in publicizing them for the world to see. If anything should be displayed at all, it is the Menkyo (teaching license) as that is really all that matters because that lets the reader know exactly what the instructor is authorized to teach. Even then, however, it should only be shared with students of the art because they are the only ones it matters to.
This is one reason I'd argue providing contact information for your instructor or governing body is more valuable than simply sharing a picture of your certificate to prove anything.
Of course, forged documents are not a new thing. A friend recently told me about a time he went to Connecticut to visit another instructor who had a certificate supposedly from Ed Parker hanging on the wall. Right in front of the instructor, my friend called Mr. Parker who not only stated it was a fake but demanded to speak with the individual. Now, Ed Parker died in 1990 so clearly fake certificates were a thing before the internet.
That is one reason Hasaka sensei, the founder of American Yoshinkan Aiki Jujutsu, started the practice of issuing generic documents for public display and handwritten documents that were considered the "true" certification. That way if someone was to ever forge a document, after he had passed there would still be a method of checking if a practitioner was legitimate by simply asking to see both copies. This was done for Steven Hatfield when he inherited the art in 2006 (see left).
Now, you will notice over the last two years I have started to release certain certificates to the public due to the scrutiny I've been under lately. But the certificates that have been released all have one thing in common - they are either from large organizations or are not something I care about being reproduced. Anything issued by my instructor is kept offline, and while he is still living there's no reason to put them out. He is very easily accessible to contact for verification of anything I claim, not to mention would have no second thought about whipping my ass if I lied about what he's awarded me.
Do I think you should be elusive about your credentials? Absolutely not. Do not claim something you haven't legitimately earned, and when asked about them you should have a way for them to be verified. I just feel that some things are sacred, and there's no reason to create an opportunity for someone to steal something you've worked for, especially when the claim of one's position can be verified with a simple phone call or email. But here's the thing...If someone is asking for pictures of your certificates and they are not a member of the same organization or a potential student, it's really up to you if you want to provide such because it means nothing to that individual. More often than not, they are asking simply to cause problems and are already approaching you with an air of distrust. And if we're being honest, if your certificates come from Japan or Korea, the person asking probably can't read them anyway!
If someone is committed to the idea you are a fraud, no amount of verification will be enough. There will always be a minor flaw to exploit or a statement to twist in order to fit the narrative. Thankfully between releasing the documents I have been, as well as putting out videos and articles to demonstrate my proficiency and knowledge of the arts I teach, the majority of the claims about me and my teacher have died down and the few people who still cling to such accusations have shown themselves to be more interested in their own story than the truth. Such cognitive dissonance is a waste of time to dispute with.