Google’s John Mueller explained on Twitter that embedded images from other sites do not count as links to these sites. You also do not have to worry about unnatural links if a shady website embeds your images.
Correct — if it's just someone embedding images from your site, that wouldn't be a link anyway, so no need to do anything.— 🍌 John 🍌 (@JohnMu) September 26, 2019
Just to be really clear, there's no need to disavow if a site embeds images from your site. We don't see those as links to a site. (Sometimes people embed images AND link to your site, in that case, links are links, do whether or not you disavow … it depends)— 🍌 John 🍌 (@JohnMu) September 26, 2019
How to find unnatural links that point to your site
Hotlinked images aren’t a problem. Real unnatural links can lead to penalties and you should remove these links. The Link Disinfection tool in SEOprofiler helps you to find unnatural links that point to your site: