icon system of KDE 3.5

This may appear “old” as a question, but I am not getting the point and I will stick to kde3.5 up to July or December of 2010, so time to “play”.
I am not getting the logic of the kde3 icon system:
I installed my proper icon-sets and they do so in
/home/myusername/.kde/share/icons
I then tried to find the other icons sets that appear to be in:
/opt/kde3/share/icons/
When I click on an icon to change it, i.e. on the Desktop, the regularly installed icons of the set appear. But there is a "drop down menu proposing various thematics under the voice “system icons”.
Now I hold also single icons/small icon sets without installation scripts, that I would like to attribute in an ordered way to the categories listed in the drop down menu.
Where can this be done? Whereto do I have to copy my single icons to appear as a selection in these drop down menus? Or is there a config file to be edited?
Thanks.

It is just that I do not understand at all the logic of the KDE3.5 icon system (with directories and localisations). :expressionless:

What you would have to do, is create your own icon theme. That would give the full flexibility you’re looking for. Change to that icon theme and you would see all the icons in the mentioned places.

Would that really be that simple as described here?
A kde icon set is just a tar.gz file with folder named as the theme, containing with certain specific folders and names for each icon, have a look at /usr/share/icons
???