Engraving is often use to enhance the appearence of a flute. The photograph below shows engraving on the lip plate of a head joint made by Ian McLauchlan. The engraving is on inlaid gold. Engraving at this particular location is often considered useful for helping the flute from slipping off the chin when perspiring.
The photographs below show engraving on a Gold Flute made by Ewen McDougall
The above photographs and notes are as accurate as my knowledge on the subject permits