Da Vinci Code objects

There are actual Easter eggs in multiplayer desert of Sandtrap. They are located near each of the pillar near the top. The eggs themselves are textured using a UV Mapping Reference texture (used to help artists paint textures on objects).

It may be a forgotten programming by Bungie Staff. For a closer look, you'll need to overload the boundaries using Trip Mines which will allow you to go through, but the Eggs are high up. You will need to go into theater mode and speed up to the part where you overloaded the boundaries. With the boundaries no longer in place you will be able to push a free camera through and go upwards to see the Eggs. It is also possible to look at the UNSC Aegis Fate using this method, and you can only get into the partially built hangar.