/usr/share/gconf/defaults/16_gutsy-wallpapers is in gutsy-wallpapers 0.22.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 | /desktop/gnome/background/picture_filename "/usr/share/backgrounds/gutsy-final-ubuntu.png"
/desktop/gnome/background/picture_options "zoom"
/desktop/gnome/background/color_shading_type "solid"
/desktop/gnome/background/primary_color "#dab082"
/desktop/gnome/background/secondary_color "#dab082"
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