There should be a way to refer to attachments to the page (images, videos, formulas, code, etc.). For example the latex filter could replace the formula with (see attachment n). This should have a link to the actual image. It should be clear that this part is not written by the user, but that it was added by the ui, so perhaps using a smaller font. When selecting and copying this part, it should actually copy the original code, not the "see attachment" part. It would be also a very good thing if by clicking on it, it could replace the "(see attachment n)" with the actual code, and backwards, like the emoticon plugin. This should available to any plugin, so that the ui results polished if you attach several stuff to a message. See comments here https://git.reviewboard.kde.org/r/111501/
Probably best to work on this in the QML rewrite. I have a plan in my head, nag me to write it down on the wiki.