Basic customizations in ubuntu 11.04 using bash

How to change the wallpaper:
in terminal type
gconftool-2 --type string --set /desktop/gnome/background/picture_filename "path/to/wallpaper"

How to change the login window icon:
in terminal type
sudo cp path/to/icon /usr/share/icons/LoginIcons/apps/64/

create desktop shortcuts:
in terminal type the follwing 2 commands.
cp /usr/share/applications/any_file.desktop ~/Desktop
chmod +x ~/Desktop/any_file.desktop

If you have screenlets installed how to run sreenlets in terminal.
type the following command.
ex:run calculator screenlet:
python /usr/share/screenlets/screenlets-pack-basic/Calc/CalcScreenlet.py

change start menu icon:
in terminal type:
gconftool-2 --type string --set /apps/panel/objects/object_0/custom_icon "path/to/icon"
gconftool-2 --type bool --set /apps/panel/objects/object_0/use_custom_icon "true"