In the book, when Digory and Polly are high up in the air on Fledge, they can see the sea in the east (a reference to The Voyage of the Dawn Treader) and mountains and sand in the south (The Horse and his Boy.) I imagine those easter eggs will be included if the budget allows. 

There are already several that are inherently part of the story, of course, like the origins of the lamppost and the wardrobe, and indeed of the White Witch, and the identity of the Professor and how he came to know about Narnia.

I'd be happy to have other little foreshadowings in there, if the film-makers are creative enough to come up with them. But I'm more concerned about them actually being reasonably faithful to the original stories and capturing the spirit of them (even if not the exact letter) and doing justice to Lewis's creation, consistently across the whole series of seven films — if this project gets further than the first one. 

Given that Gretta Gerwig likes to include meta references in her movies, I wouldn't be surprised if there are references to C.S. Lewis' own life.
I think someone has already raised that Digory may be from Ireland, like Lewis. I wouldn't be at all surprised if Digory takes on biographical attributes of Lewis that weren't present in the books (or at least not obvious in the books).

Where Lewis describes England as looking drab in Surprised by Joy, it wouldn't surprise me if something like this was used instead of Diggory's description of London as 'a beastly hole'. 

Well I guess we already know two Easter Eggs:

• The movie being set in 1955, the same year as the book was published.
• A background poster in the first set photos bearing the names of Harold & Isadore - Greta Gerwig's two children.

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Hmm, some Easter eggs of the other Narnia stories would be idea. I think it raises the question of how and where.

The Walden film trilogy did kind of have an Easter egg. In LWW, the wardrobe had the carvings of The Magician’s Nephew (which I’ve never noticed the first time I’ve watched it); in PC, in the scene with Aslan’s Howe, it had paintings of the events of the first film, which was neat; and in VDT, it had the world of Narnia map, and even the torch that Edmund had left in Narnia in PC (you know that line, “I left my torch in Narnia”), and apparently Caspian have saved it for him. (Not in the book, I know, but still a pretty neat detail.)

So with The Magician’s Nephew being released this next year (it’s going to be here before we know it), I wonder how the filmmakers will stitch together the rest of the universe. Perhaps, in the scene where Digory and Polly are flying on Fledge’s back, they’ll glimpse of the Eastern Sea and where Cair Paravel would be built, a glimpse of Archenland and further south of what would later be Calormen, a glimpse of beyond the Western Wild where Telmar would be, or even a glimpse of the Wild Lands of the North where giants would later trod—just a fleeting nod to the world’s eventual shape.

On existing Easter eggs, there is also a quick reference to the Magician’s Nephew in the scene where Professor Kirk talks to Peter and Susan in the Waldon Lion, the Witch and the Wardrobe. At the very start of the scene, the professor gets some tobacco to put in his pipe. The container that he gets the tobacco out of is shaped like a silver apple.