The best place to post this type of question is to the Customising & Remastering forum. Check out the HOWTO I made http://www.knoppix.net/forum/viewtopic.php?t=13867 or see the docs for the remastering HOWTO http://www.knoppix.net/docs/index.ph...masteringHowto.

You should be able to create a script that launches vncserver. There is the issue with the vncserver password as you will either need to capture it or have to enter it everytime the script is run. I would store that script (myvnclauncher) in /etc/init.d/. Then I would create a link to that script in runlevel 5.
Code:
ln -s /etc/init.d/myvnclauncher /etc/rc5.d/S80myvnclauncher
That script would be executed right before Knoppix starts up KDE.

If you want to start the vncserver after KDE starts up you will probably have to edit the /etc/X11/Xsession.d/45xsession script as it controls how & when KDE is loaded.
I hope this helps.
James