News Courtesy of rankranger.com:
On July 13th, our Mobile SERP Feature Tracker began showing an increase in page one SERPs showing Image Thumbnails (mobile). By the time the data leveled off, mobile Image Thumbnails had gone from appearing on 15.7% of all mobile page one SERPs to an all-time high of 44.5%. That’s an enormous increase, a 183% increase to be more specific.
To give this data some context, the most notable increase in the SERP feature, prior to the one just seen, occurred in September 2016. At that time, mobile Image Thumbnails had gone from appearing on under 1% of all mobile page one SERPs to just over 10%.
Since then, the feature has fluctuated between showing on around 7% of mobile page ones to upwards of 15%. At no time during this prolonged period had the feature ever gotten close to the levels we’re currently seeing.
Ryan’s Take 
If there were any doubts about mobile search priority for Google, these new statistics should eliminate them. Since thumbnail images aren’t a new feature, it would be easy to miss such an increase. Testing out some keyword phrases, it is now very apparent that thumbnails are a lot more prominent than they were several days ago.
The thing I find interesting is that even old web pages have returned image thumbnails in mobile searches. Using the longtail keyword phrase car inspection in maryland, as suggested in the article, returns a web page all the way back from 2010 with a thumbnail. At that point in time Schema markup wasn’t yet introduced. Although, upon further inspection, the source code did reveal an image markup tag. Perhaps, added to the page (and the website) later on through an automated script. I have to believe that Google isn’t pulling images directly from a web page but does, in fact, rely on Schema.
Regardless of how it is implemented, this increase in thumbnails appearing should also increase the click-through ratio of affected results. Desktop search results almost are starting to look archaic compared to their mobile counterparts. Keeping all this in mind, choosing an appropriate featured image for important pages and posts should be treated with higher regard. It’s just another asset that can be used to entice potential visitors to click on your page in the search results.
