Yes, we "clean up" all HTML, need some core updating (replace img by alt, or by src if tehre are no alt).
But actually, you can use:
<img src="yourpicture.png" /><span class="hide">The text</span>
In sub question
Assistance on LimeSurvey forum and LimeSurvey core development are on my free time.
I'm not a LimeSurvey GmbH member,
professional service on demand
,
plugin development
. I don't answer to private message.