There is a syntaxe error in extension/eznewsletter/design/admin/override/templates/embed_image.tpl

':' should be replace by ';' in

{append-block scope=global variable=$imageFileList}{$image_variation.full_path}:{$image_variation.url|ezurl(no)}{/append-block}

Steps to reproduce

When you create a newsletter with an article containing a XML Block, If this block contains an image, this image won't be visible in the e-mail (HTML format).