And how do you prove the certificate is authentic?
You can prove any given bitcoin is yours just by transfering exactly the amount requested by the viewer from one address to another (also yours). It costs whatever single transaction costs and takes exactly as long. You can do it as many times as you need, and you don't need any third party, just a computer connected to the internet that is sufficiently secure for you.
Just as you say, you don't want to verify ownership every time someone views your thing. You do it once with a trusted 3rd party, get a certificate or whatever you want, and hang it next to your piece.
If you now wanna show off your bitcoin worth, get a e-ink display connected to a raspberry pi that shows the current value of your bitcoin wallet. Have the certificate you acquired for this wallet right next to the e-ink display. Now exactly the same as if you were to show off your Van Gogh.
Bit false of you to compare showing a Van Gogh with verifying a bitcoin wallet. More appropriate to compare verifying a Van Gogh with verifying a bitcoin wallet, and we both surely know which one is faster and more reliable.