Star Wars Episode 6: Return of the Jedi - Helmet Drums
At the end of the movie when the Ewoks and our heros are celebrating, there's a scene when a Ewok is playing stormtrooper helmets as drums, but if you look even closer you'll also notice Vader's helmet is also used as a drum. Wasn't he wearing it in the funeral pyre? Did Luke get sentimental and pull it out just in time then decided it would make a great keepsake?
...ah...I believe that if studied closely, 'twould be a Death Star Gunner(TM) helmet. Although you are correct in your immediate assumption that the only Death Star Gunners(TM) were on the Death Star(TM) itself, meaning that it is sort of a slipup, since the only way an Ewok(TM) could have gotten hold of it would be to snatch it(TM) as it plummeted from orbit. It's wrong, Jim, but not as we know it...
The helmet you are refering to could have been a few different things.
Number One- The death star gunner's Helmet.
Number Two- The shield generator operator's helmet on Endor.
And possibly the Tie fighter poliot's helmet.