In the early 1980s, Washington’s National Cathedral was losing relevance with the younger generation. In an effort at outreach, they partnered with National Geographic to hold a “Draw-a-Grotesque” competition for schoolkids. (A grotesque is a gargoyle, without the water-draining feature; it’s purely decorative.) The winning designs would actually be carved in stone and installed on the cathedral.
The Grand Prize winner was of a toothy man; the first and second runners-up were of a girl and a squirrel. But it’s the third runner up that today is most notable. Thirteen-year-old Chris Rader of Nebraska submitted his drawing of Darth Vader’s head. “I read that grotesques are often demons or monsters,” Rader explained. “Darth Vader is a lot like a demon. He’s evil, so I thought he would be a good choice.”
A stonemason was hired, and all four designs were carved and added to the cathedral.
While you can’t make out the Dark Lord of the Sith in long shots of the cathedral, an on-site placard provides guidance for visitors with binoculars.
I imagine Lucasfilm let this one slide.