You can add a theme on your town, the kids in your classroom, your pet, your family members!
And you can choose to make the theme available for you (in your personal Pysycache directory) or for all users (in the theme directory of Pysycache)
See the FAQ of each activity for learn how make your theme
You'll find the script-fu for gimp in the doc/Script-Fu/scripts directory.
You have to copy the content of the scripts directory in the script directory of Gimp:
/usr/share/gimp/2.0/scripts for Unix users
c:\Program Files\gimp-2.0\share\gimp\2.0\scripts for Windows users