Lock
shortcut: %windir%\System32\rundll32.exe User32.dll,LockWorkStation
for a suitable icon see %SystemRoot%\System32\shell32.dll


Reboot
shortcut: %windir%\system32\SHUTDOWN.exe -r -t 10
for a suitable icon see Google Image Search for reboot


Hibernate
shortcut: %windir%\system32\rundll32.exe powrprof.dll,SetSuspendState Hibernate
for a suitable icon see Google Image Search for hibernate


Shutdown
shortcut: %windir%\system32\shutdown.exe -s -t 00
for a suitable icon see %SystemRoot%\System32\shell32.dll