Make sure that the image is centered in the main content area.
If there’s an image that represents the query well, Google is likely to show that image.
Make sure the overall context of the page matches the search query.
The overall context of the page should match the target search keyword and query.
H1 tags also need to be relevant to the title.
These images should be optimized with alt tags and title tags that match the relevant search terms.
Important images should be above the scroll fold.
Image URLs need to allow easy crawling and indexing by search engines.
gif formats with 16×9, 4×3, and 1×1 aspect ratios.
Images should be 1200 pixels wide and in.
Only images belonging to the article should be specified.
Every page needs to contain at least one image that represents the marked-up content.
Here’s what Search for Developers, a guide from Google, recommends for using structured data, or Schema, for images found in articles: However, we did find some articles that might be helpful. So far, Google hasn’t released any instructions on optimizing for these mobile image thumbnails. This seemed to work the best across the board. The image file name, alt-text, nearby headings and body text contained the target keywords, giving Google multiple hints as to what the main image is for any matching queries.
Made sure keywords were close to the image.
Turned the background image on the page to an img tag with optimized alt-text.
Only a couple of other results had images for that query anyway. On the mobile search results page (SERP), the query, “Diesel Delivery PA” had no thumbnails at all while “Diesel Delivery” showed the featured image as the thumbnail. There was no image at all displayed on mobile after enabling. However, it’s still not the preferred image. In response to this, Google showed the first image on the page instead, which makes more sense. Here’s everything we tried to get our desired thumbnail image displayed for the “diesel delivery” search term: