I think when ubuntu 9.10 released system menu icons was hidden with default release, as same as with ubuntu 10.04 beta 1
it’s old trick for who don’t know it so there are two ways to get these icons back.
open terminal and type
gconftool-2 --type Boolean --set /desktop/gnome/interface/menus_have_icons True
open configuration editor from system tools
if you can’t find it open terminal and type
then go to Desktop –> Gnome –> Interface
you will find “menus have icons” make this value true