In the init field of your empty flagpole put:
flagpolename setFlagTexture "usa_vlajka.pac"
or
this setFlagTexture "usa_vlajka.pac"
This of course is the US flag
The Flags.pbo in your addons folder has a whole list of flags you can use for just about any country you care to think of.
These are all in .jpg format.
So:
this setFlagTexture "Scotland.jpg"
would give you the St. Andrews cross. ;D ;D
Planck