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/2.0/scripts/bovinated-logo.scm. (where /usr
is your GIMP installation directory.)
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 may
take quite a while to render on a slow computer.)