Public Domain sample photo:

https://commons.wikimedia.org/wiki/File:Kobe_Bryant_8.jpg



Poster sample on sale:

https://www.amazon.com/Basketball-Painting-Posters-Memorabilia-Decoration/dp/B08BS3XBF2/ref=sr_1_10?dchild=1&keywords=lebron+james+poster&qid=1605596576&sr=8-10

I don't know how they sell those, and in my opinion (I am not a lawyer) selling a representation of Lebron James or any other recent celebrity, could get the artist in trouble. Your example is a good one, where someone painted from an original photo, (or for all we know, filtered an original?) which is someone else's creation. I suppose some will argue it's a new original work of art, but the source material is copyrighted. So the original photographer could have rights.

Even with that, a personality owns the rights to their own likeness. It's blatant that the artist is also making use of his name. This is just a mess.

Just altering something, doesn't make it a new work. Yes some artists have made their name doing that, which I think is kind of low. The name now is "appropriation art". Some cases the artists have won, some they lost. Depends on the judge. That's how vague the law is, and how open to interpretation.

Anyway, now that you have explained more, and even though you did say poster in the original, it does make a difference, what you are doing and what you are making. If your original is clearly public domain, not CC, expired copyright, you can pretty much do what you want with them.

With recent changes to the laws: Copyright happens automatically, the minute you set something into a "fixed form" � even if that fixed form is a doodle. You automatically own the copyright to any creative work of art you produce, the minute you produce it. So does everyone else. That's why I linked and mentioned before 1925, and more complicated are the changes to the copyright laws since the 1970s.

Easiest place to start is, how old is the image you want to use for the poster. Before 1925, you're on the way. Next would be, does the subject claim rights to their name or personal likeness, or the estate of that person does. Then research.

Yes you can make and sell a poster of a PD image. Just for an extreme, I could make and sell prints or posters of this image, Dorthea Lange, because it's public domain.



Or this one by Ansel Adams



Since this is the Microstock Forum, most agencies won't accept these. Maybe resale isn't illegal, but they aren't interested in a collection bloated with PD images. The laws and what agencies will accept are not the same. Agencies make their own rules, beyond the laws.