Da Vinci Code objects
From Halopedia, the Halo wiki
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.
Sentinel Beam Guardians
You should also note that each of the pillars encompassing the map have one of these. Some even have different textures. A theory about the eggs is that whenever a player is in the mine field but for some reason won't die, then the easter eggs will shoot sentinel beams at you. It was proven that the Easter Eggs are in fact what triggered the mines in the minefield acting as the guardians of Sandtrap similar to the turrets on Snowbound. There is a video proving this theory. The video can be found here.
The same sentinel beam has been confirmed to be on the upcoming Mythic Map Sandbox. In several screenshots from the Bungie Weekly Update, it showed players outside of the boundaries being hit and killed instantly by the beams. The beams on Sandtrap are less obvious and are meant to trigger the mines and not to directly kill the player.
Because the same Sentinel Beam Guardian appears on Sandbox, it may be possible that these Easter Eggs will also appear on Sandbox. Another possibility is that the Easter Eggs on Sandtrap were unfinished by Bungie and they forgot to go back and finish it so it was left as is. Since the beams were emphasized on Sandbox, the eggs may have been fixed and completed on Sandbox. Therefore, it may be possible that when Sandbox is released, players may be able to see what the Easter Eggs were meant to be.
The Sentinel Beams
It appears that the Sentinel beam will appear on Sanbox like it appears on Sandtrap. The only difference is that it may be more deadly.
