Now for something completely stupid and it might not even be an Easter Egg, we might just be seeing things.
On my first playthrough of Twilight Princess, my fiance' watched me as I went through the Goron Mines. Suddenly, he exclaims to me "ELO!"
I ask, "Where?"
"Above that doorframe."
I looked where he indicated and, sure enough, there appeared to be the letters "E L O." The way they looked, however, I could not tell if they were intentional or just part of artwork/cracks, something that his eye just caught.
There is the possibilty of it being intentional, however. For those who do not know "ELO" is the common abbreivation for Electric Light Orchestra - a musical group famous for, among many songs, a song called "Twilight."
And, yes, that song is known worldwide. There is a music video to that song that is very famous in anime-fandom circles, done for a Japanese anime/sci fi convention back in the 80s by the people who eventually formed Studio Gainax. If you are wondering about, it just Google or Youtbue "Daicon" and you'll find it.
Unfortunately, I do not have any screenshots and I can't remember where exactly in the Goron Mines this doorframe is.