It seems that Google has increased the number of thumbnail views in mobile search results snippets. A RankRanger report, which I covered yesterday in Search Engine Land, shows that 75% of search results tracked include at least one image thumbnail in the results, an increase from 40%.
While Eric Hedekar of Moz shares this opinion with the 75% figure, he said that he thought it was like that for quite some time. Although the number of thumbnails has increased significantly in a set of specific search results.
No substantial bump in the number of SERPs with thumbnail results on our side. Always stable around 70-75%. I can confirm that the amount per SERP has almost doubled on the 7th, but has decreased since (no increase today).
– Eric Hedekar (@EricHedekar) March 11, 2019
Google has long been displaying image thumbnails. Google even tests them on the desktop results.
Be that as it may, here are the RankRanger diagrams, this first shows the increase in the number of times they appear for a given query:
 The second indicates the average number of thumbnails of images on page one; on March 11, they rose to five:
Google communicated to us on Search Engine Land "We are still working on new ways to improve research with useful visuals and we encourage site owners to enrich their pages appropriately. "
Here are some screenshots of what this looks like:
Discussion on the forum at Twitter .