I was wondering if Journal is the app to use as a log-book of my work,
the missing piece (I maybe did not find it) for me is the capability of inserting images in the text.
Do you know if it is possible?

Do you know if not an alternative to it that I could use for my purposes?

Regards
Lucat

Unfortunately Journal does not support inserting images at this point in time.
Only other thing I can think of is a word processing document however.

There is also Basket, but there hasn't been newer version since September 2010.
Debian package works (except Kontact integration, without which Basket is useless for me), so perhaps it will at least compile against newest KDE. But using apparently unmaintained software may not be the wisest idea.

Apart from that, I don't know any KDE alternative.

Outside KDE/Qt world, there is zim. I has been using it as note-taking program for quite a long time. There is even plugin for inserting image from clipboard.