dan1487, good to have someone report having seen these. They aren't completely new, but I suspect that they will become important. There have been reports that Google has been testing image carousel sliders in its mobile interface since roughly May 2017. What is newer is that they're now also product image related and not always AMP pages.
Barry Schwartz reported very briefly on these Wednesday in Search Engine Roundtable, describing them in his post as "somewhat new, based on how you look at it." He posts a screen capture of a current carousel slider in mobile, though not product related. The blog Barry cites as a source does show product results.... Newish: Google Image Carousel Sliders In Mobile Barry Schwartz - Sep 13, 2017
Google's got a whole section on Carousels for mobile in the Structured Data section of Google Developers, which is an area that went through a big reorganization just at the end of May, 2017. So, I assume that markup is tied in with what you've seen, and that using proper markup could be helpful in achieving the kind of display you're talking about. Signals of site quality would also be important.
Here's a page which might be particularly relevant, as is other documentation in this developers area.... CAROUSELS Google Developers - Guides
Note that Google treats Carousels as lists of images, which... if they were to be pulled from the same page... would require two or more images of the same type
on a given page, with the images relevant to what the page is saying, and different enough from each other that they essentially tell a story. That story, of course, should relate to the page.
I'd advise considering this an interface test in progress, albeit it's a test that might stick for a long while.