The Top Stories Slider, Blog Posts & Pages and the News Boxes macros generating, like the original Confluence Blog Posts macro, an excerpt from the first couple of lines of a blog post (unless the actual Excerpt macro is used, then the content from the Excerpt macro body will be used instead). Due to a bug, that was introduced in Confluence 5.4, images and links are not rendered properly any more. Instead of the actual image, the name of the image is shown and with links, instead of the rendered clickable link, the URL of the link is displayed.
This Confluence bug has been already reported to Atlassian, see CONF-34197 - Blog Posts Macro renders URLs as text when content = excerpts and post contains no excerpt.
Instead of letting Confluence generate the excerpt, using the beginning of the blog post content, you can use the Excerpt macro to define an excerpt including links and pictures.
Why is the image name displayed instead of the image itself? (Enterprise Theme for Confluence)