Some users, hiding behind pseudonyms, made an apparent attempt to sell the pictures or to trade them with fellow hackers for others.
Security Hole Tech news site The Next Web reported what it said was evidence that hackers had found a weakness in Apple's "Find my iPhone" service, an app that tracks lost or stolen handsets.
Apple has patched the alleged hole, the report said, but not before news of it spread in the hacker community, perhaps allowing unscrupulous strangers to access private online data.
But other reports suggested that the pictures could have been collated from multiple sources, perhaps not including iCloud at all, and may have been gathered over several years.
News site Deadspin said it had been contacted in early August by a source claiming he had been offered the pictures for sale.
The scale of the hack, and the targeting of women in the public eye, quickly revived the debate on social media about privacy concerns and about misogyny on the Internet.
The scandal also posed a public relations challenge to tech companies, who have been marketing online storage like iCloud, DropBox or GoogleDrive as a safe haven for users' private data.