Originally Posted by Streadmob
Iíd like to mention an illustration located in another chapter, and allow the reader to click on its name to go to it. [...]
Iím using Calibre to construct e.g. mobi files from html and itís going ok.
Calibre is a great converter, but IMHO it's better to create an ePub in Sigil first and then convert the ePub with Calibre or Kindle Previewer.
This has the advantage that you can use Sigil's integrated FlightCrew validator to check for structural errors and other issues before the .mobi conversion.
I'm assuming that you want to use images as chapter headers. If that's the case and all chapters are in the same .html file, you could try the following:
<p><a href="#ch1">Chapter 1</a></p>
<!-- more TOC entries -->
<h3 id="ch1" title="Chapter 1"><img alt="" src="ch1.JPG" /></h3>
(If you use Sigil, you'll need to use <img src="../Images/ch1.JPG" />, because Sigil stores .html files and images in separate folders.)
BTW, using header tags with title attributes will allow you to automatically generate an .ncx TOC once you're done with the book.