It does not conver any legal ownership over the image. It does not confer copyright. Anybody else could come allow and create a new series of NFTs that include a token pointing to the same art, and sell it too.
NFTs are basically equivalent to those pieces of paper that claim ownership over a plot on the moon that get sold. Anybody can make them and sell them, and they have zero legal ramification.
The only thing that makes a particular NTF that points at a work of art special is if it is endorsed by somebody.
This can have meaning though. While anybody can make baseball cards for any player for any year, only those made (endorsed) by certain companies have any value in the collector's market (and only certain players and certain years).
But even then at least you really do legally own a physical piece of paperboard.
NFTs are more akin to owning a unique item in a video game, except at least with those you can usually use the item.