Hi Kallie,
I think the Lithium modules doesn't support such a functionality out of the box. Per default each attachment is related to a blog post and therefore they are stored within the Lithium infrastructure.
One solution could be using hidden markup and JavaScript snippets:
You could add something like this
<div class="lia-js-hidden" data-attchmenturl="YOUR_URL_GOES_HERE"></div>
via the HTML-Edit-Mode to your post.
A small JavaScript (which is added to the BlogArticlePage quilt) could crawl the content for the hidden content and the render the data as you prefer.
To make adding the hidden markup it bit more comfortable to users, you could add customization (a button for example) which injects the stuff above (and asks the user for the attachment url).
Regards,
Christian
