its not directly supported fo rnow but this is what you can do: upload the photo/image that you want to embed in the blog in one of your albums. From the page that you see right after the upload completes successfully (single photo page), copy the image by selecting the image are and Ctrl+C (will provide a link soon to copy the url to clipboard) Now you can do Ctrl+V in the blog page editor and you have the image hosted on minglebox and available on your blog.

Who said, you can't. Use the image tag.