Press the button next to "Font:" and select a nice scalable font.
Press OK.
And you have a full-fledged logo.
The source code of this script can be seen in
/usr/share/gimp/1.2/scripts/bovinated-logo.scm.
You can play with the other scripts in the
Xtns
->
Script-Fu
->
Logos
menu and view their source code. (my personal favourite is Frosty, which is
quite heavy on CPU and time).