In one of my blog
techiemate.com i faced an issue with its featured images that wasn't displaying on the index pages of
blogger blog. And then i found the solution to fix it. And now i decided to share how i fixed it with all of you because you might have same issue with the same as recently Google blogger changed its protocol to http to https even it changed to the new images you upload. You can check your blog's post's images where you will see the URL of the image which will be start with HTTP and then go to the new post and upload the image and look for the Image URL it would be start with HTTPS and this is what stopping featured images to show up on the homepage and other index pages.
Also see : Show each blogger post's featured image on index pages (Different than inserted into the post)
OK so, if you are facing the same issue with your blog, then all you have to do is to remove "S" from the protocol of a specific image URL which you want it to be displayed on the index pages.
as an example, when you upload an image to the post, its URL should be look like this :
https:https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYyyySv9j9GC3PpJiScSJCShlgAEol9u9KlghJooJsXGqiytQtJHt_Qhvu2gj7NivL9RRs6T1Kv0TnNjzyeGGJXMtiqogW-4fUKvfxdJdzfx2mC1rxRW00STUGWZlnOHP1jSxuFR49NNQ/s640/1-ravi-varma-paintings.jpg
As you can see in above red colored text in the URL, which you have to change with HTTP and it would be look like this :
http:https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYyyySv9j9GC3PpJiScSJCShlgAEol9u9KlghJooJsXGqiytQtJHt_Qhvu2gj7NivL9RRs6T1Kv0TnNjzyeGGJXMtiqogW-4fUKvfxdJdzfx2mC1rxRW00STUGWZlnOHP1jSxuFR49NNQ/s640/1-ravi-varma-paintings.jpg
That's all.
Still if you have any questions about the same, feel free to ask by commenting below. Thanks !