You can add a new option for the window frame setting in the Theme preference tool. Window frame options reside in the /usr/share/themes/option-name/metacity-1 directory. The typical structure of a window frame option in the file system is as follows:
/usr/share/themes/option-name/metacity-1/metacity-theme-1.xml
/usr/share/themes/option-name/metacity-1/*.*
Typically, a new option for the window frame setting is supplied as a .tar.gz file. To install the new window frame option, unzip the .tar.gz file, then untar the .tar file into the /usr/share/themes directory.
Users can install their own options for the window frame setting. If a user installs an option for the window frame setting, the option is stored in the $HOME/.themes directory.