I have to agree here for the most part (again, not a lawyer, so this isn’t legal advice).
You can’t copyright individual components of certain creative works. As @ProfSrlojohn said, that would mean anyone producing works that require materials or components could never be legally made.
The best, but imperfect, example of this is music. No single person can own an individual musical note. If that were the case, that note could never be used in any songs. Instead, people can own certain arrangements or configurations of those notes (in other words, they own the rights to their own songs).
Now, it’s not quite a perfect analogy because LEGO does own the actual design of the LEGO brick and any other piece they produce. In this case, the components themselves are owned by an entity, but any creation you make with them is legally your work.
With MOCs, though, it’s a bit weird. People like to give credit for particular piece combinations (the “Gringat hand” is the most popular in the Bionicle community, for instance), but personally I’d argue that it isn’t strictly necessary, but a courtesy thing.
I don’t know, it’s an odd situation. If someone recreates your MOC and passes it off as their own, can they do so legally? It might be a hard case to make.
But, for your question, I don’t think LEGO can or would do anything legally about a picture of a custom LEGO creation.