Bloglovin' is looking for images associated with the posts in your blog's RSS (See "What is RSS?").
If your images are not included in the RSS, they will have to be added to this feed in order for Bloglovin' to be able to find and display them. Please contact whoever is responsible for the technical issues of your blog for further assistance.
If the images are already included in the RSS but still not showing up on Bloglovin', they might be too large. For optimal quality and loading time, make sure the images are at least 310 px in width while remaining under 2 MB in size.