Just ran across this nice little tool: Parasite:
Allows you to dynamically change Gtk widget attributes on a running GRAMPS program (or any Gtk-based program).
This is a very nice way of testing different Gtk settings without having to restart GRAMPS.
Here is what I did to try it out on Fedora:
# get the things necessary to build it:
yum install git-all libtool gtk2-devel python-devel
git clone git://github.com/chipx86/gtkparasite
# build the sources:
# install (in /usr/local)
sudo make install
# add the libs to my path:
# run it:
GTK_MODULES=gtkparasite python src/gramps.py
Then I clicked "Inspect" in the Parasite window, and clicked on the GRAMPS window. Change settings of the widgets and see results. I've only tried it briefly so far, but looks like it will help me as I am lame with gtk.