Though you do have multiple images within the individual blog post item (CMS Item), you’re not referencing them on your page itself. For example, your banner image up top (the one that is showing) is being pulled from the Main Image field in your CMS Item. However, though you have other images uploaded to the CMS Item, you have no image fields or divs on the page that reference those images.
Check out the following video:
I copied that div up top and pasted it multiple times, and simply just changed the background image of the div to reference those other fields. Further, I also added an image field and pulled the image that way as well.