Thumnail images that appear beside search results in google

When I search on google for topics related to my website, my posts and a few others on the same topic come up. The other pages all have thumbnail images from the page displaying next to the search result, including a blog I write for. However, my blog posts and pages do not display this thumbnail. Why? How can I change this? Is Squarespace a massive dud for images?

More information and additional ranting:
I'm a photographer building a website with fairly unique images. I am trying very hard to get my images indexed by google and to display in search results, as they may be one of the only images of these subjects to exist and I want people to find them and be directed to my website.

This is proving very difficult and I am wondering if Squarespace was the wrong choice.

After a lot of work, I am having some limited success - however sites from people I know using Wordpress or Wix etc appear to be outperforming me with much less effort put into SEO. Once of my most successful pages is a blog post I did in March 2022 where several images in the gallery on this post are indexed and showing up in google search results. The post I published a day later has only one image indexed and it appears to make no sense why. When I search for a particular image using keywords in its filename, caption and alt text, random image results appear from the same page but infuriatingly, not the image I am looking for. Not to mention I had to entirely ditch "portfolio pages" as google could very rarely see them.

I don't know if this also has to do with the thumbnail problem, but the whole image management appears to be a total mess. Please advise.

any one can help us same issue i am also facing no images is index in google till now.i design all images my self in high quality but with no reason these images are not index any body help me in this regard highly appricated

on demand i can share my link of website which are facing this issue of no idexing of images thanks