Here is the content of the file named xfcegui_module.txt use to build Impilo 11.04.

#
# Modules for minimal GUI install
#
xfce4
xfce4-goodies
gdm
tango-icon-theme

#
# Modules for printing support
#
cups
cups-driver-gutenprint
foomatic-filters
ghostscript-cups
cups-pdf
foomatic-db
system-config-printer-gnome