Google seems to be testing or launching (or maybe it is a bug) showing a more images section within the featured snippets. I had a couple of reports of people seeing this over the past 24-hours, I personally cannot replicate it.
Here are images from @MordyOberstein and @type_SEO:
In addition to this, people are seeing alternatives to this, like we saw the featured snippet image carousel back in November but also other variations:
Spotted something like this on mobile last week, featured snippet and multiple image. What's the result like on mobile Mordy? Cheers 🧐 pic.twitter.com/nxx7NZ3Hyc
— Andy Simpson 🔍 (@ndyjsimpson) July 2, 2019
On mobile, I get the "collage" carousel.... the bubble filters (w. video indicated) & then a video box with the video from desktop being shown as a large lead video. pic.twitter.com/DGApyLkJuu
— Mordy Oberstein (@MordyOberstein) July 2, 2019