Update: Bungie has confirmed that this is the true Sandbox, and has now posted a high quality picture on their gallery of it.
Rumor is that the image (below) is of Sandbox, which is a new map from Bungie's Mythic Map Pack that is set to release with the Halo Wars Special Edition.
There is no confirmation that this is real but if you remember that drawing that was posted on the Bungie.net weekly update it resembled Sandtrap at night and I think this is the perfect match.
More details to come as they are available!
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