You can install a new option for the controls setting in the Theme preference tool. Controls options are in the /usr/share/themes directory.
The option file for a controls option is located at /usr/share/themes/option-name/gtk-2.0/gtkrc.
The image files for a controls option in the file system are located at /usr/share/themes/option-name/pixmaps/*.*.
Typically, a new option for the controls setting is supplied as a .tar.gz file. To install the new controls option, unzip the .tar.gz file, and untar the .tar file into the /usr/share/themes directory.
You can install your own options for the controls setting. If you install an option for the controls setting, the option is stored in the $HOME/.themes directory.