/usr/share/themes/Natura/openbox-3/ is in openbox 3.5.2-8+deb8u1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/themes/Natura/openbox-3/close.xbm
/usr/share/themes/Natura/openbox-3/close_hover.xbm
/usr/share/themes/Natura/openbox-3/desk.xbm
/usr/share/themes/Natura/openbox-3/desk_hover.xbm
/usr/share/themes/Natura/openbox-3/desk_toggled.xbm
/usr/share/themes/Natura/openbox-3/iconify.xbm
/usr/share/themes/Natura/openbox-3/iconify_hover.xbm
/usr/share/themes/Natura/openbox-3/max.xbm
/usr/share/themes/Natura/openbox-3/max_hover.xbm
/usr/share/themes/Natura/openbox-3/max_toggled.xbm
/usr/share/themes/Natura/openbox-3/shade.xbm
/usr/share/themes/Natura/openbox-3/shade_hover.xbm
/usr/share/themes/Natura/openbox-3/themerc