I have installed this add-on (http://addons.elkarte.net/2014/11/Inline-Attachments/), which allows inlining attachments in posts, using the following tags:
[attachimg=n] (full size image)
[attach=n] (thumbnail image)
[attachurl=n] (link with view/download count)
[attachmini=n] (simple link)
Where n is the attachment number within your post, starting with 1.
Note, there is a slight issue with the tag, in that it cannot be previewed. You'll have to trust that it works when you post.
Inlining an attachment with one of these tags will also remove it from the usual list of attachments appended to the post, so if you inline tag all of your attachments, no attachment block will be displayed after your post.
It doesn't work. For example this post:
How to do this correctly?
I have filed an issue upstream (https://github.com/Spuds/Elk_Inline_Attachments/issues/2) with the extension developer. Hopefully it will be fixed soon.