After you adopt the now called "Mystery egg/Mystery egg(s)",maybe you can make it so that it looks like the pokemon i bit.
I'll make an example with icons i made
But here is where it gets interesting,they can only see the actually color and density of the egg "After" it's adopted.But Maybe theres anything thing i had in mind,if they have no idea which pokemon it is,dont let it have actual egg look after adoption,add an "Enchance stone" to the shop,maybe set it at the price $20 since people will love to at least get the idea after using the "Enchance stone" to show actual image.Keep it at default image until Enhance stone is used on the egg
Durant egg
Cyndaquil egg
It'll be great because since we dont have the actual name for the eggs anymore,people can get the idea like "Ok let me use this enchance stone and...its white and red...oooohh maybe its a heatmore..ooohh oohh maybe its a delibird" it will increase excitment.
Thanks for reading,and this is a suggestion...please consider.
Bye