Yes, and the people checking the painting could fraudulent.

Using a blockchain does not prevent:

Events that are happening that are not registered Events that didn’t happen are registered Wrong events are registered

So far the only ‘reasonable’ use case seems te be cryptocurrency, as long as nobody controls more than 50% of the chain. Then still I don’t get why entries in a secure distributed database should be worth anything. Anyone can start a coin or a fork of bitcoin, so why do they have value at all?