My problem is:
I have to change the close icon in the title bar, the problem is that I should not install a new theme, I have to edit the icon.
In which directory holds these icons?
What should I do to update the change?

S.O: openSUSE 11.1 (x86_64)
KDE: 4.1.3 (KDE 4.1.3) "release 4.9"

I believe that the close icon in the window decoration is drawn programatically and is not stored as a file on disk. Is there a particular reason why the close icon needs to be changed?

HELLO

It is very necessary to change the icon as it is a requirement of a job.

How extensive are the required changes?

You could consider modifying the Oxygen window decoration code to draw the needed icon, creating an Aurorae theme ( no C++ involved ) or using another alternative already existing window decoration ( or Aurorae theme )

It's probably easier to modify the deKorator theme Oxygen for deKorator. It appears to use the old Oxygen button, but you can get svgz for buttons that look like the new ones from this theme (and export to png or whatever deKorator uses).