I searched around, but all of the googles of easter eggs for this film generally turn up easter eggs for more recent DC films, or nods to STM in those newer films, but not easter eggs contained in STM itself.
Just two things I was wondering about:
1) In Lex Luther's park place subterranean lair: at one point, Otis comes out from behind one of a set of screens showing a tropical paradise. While he's fumbling through them, we see a cut in the tropical footage that goes to a reel countdown and a test pattern showing the image of a woman. Is that woman special, or just a common face in such test patterns?
2) In Lois Lane's apartment, on a table near he front door, is either a book or a picture frame with a mans face on it. It gets enough frames in the film that I feel it must have some meaning for Donner or someone else on the film -- any ideas?
In my searches, I did run into the following easter egg that was new to me. Perhaps it is to you as well. See the text below this image:
(In event of no image: shows a young girl in a train car pointing out window, with parents not noticing the teenage Clark Kent racing past the train.)
"Lois Lane first appears as a little girl in Richard Donner’s ‘Superman,’ who spies a young Clark Kent outracing her train (“faster than a locomotive,” etc). In the scene Lois’ parents are played by Kirk Alyn and Noel Neill, the movies’ first Superman and Lois Lane, from the original 1948 serial."
Credit for text: http://screencrush.com/dc-movie-easter-eggs/