Hi ztealmax
Basically, what you want to do is set up a temporary directory structure containing the files that mimics how
it would look in a running system. For example, if the package requires a file located in:
/usr/local/share/icons/Rodent/48x48/apps/xfce-printer.pngyou could copy it to:
/tmp/xfce4-themes/usr/local/share/icons/Rodent/48x48/apps/xfce-printer.pngAdd any remaining paths/files under  /tmp/xfce4-themes/  that you want installed with the package.
Now create a file called:
/tmp/xfce4-themes/usr/local/tce.installed/xfce4-themesIf you need to perform any commands when the package is installed, add them to xfce4-themes, otherwise,
leave that file empty. Finally:
sudo chown -R root:staff /tmp/xfce4-themes/usr/local/tce.installed
sudo chmod -R 775 /tmp/xfce4-themes/usr/local/tce.installed
cd /tmp
mksquashfs  xfce4-themes xfce4-themes.tczCopy the  xfce4-themes.tcz  file to your  tce  directory and add  xfce4-themes.tcz  to your onboot.lst.