I personally would like to see Halo 4 have a night map and a medium sized Forerunner jungle map. For the jungle map, think about a mix between Zanzibar and Guardian with a little less verticality to it than on Zanzibar and a little more fauna over the structures. Also with little less open enviroments.
As for the night map, for some reason I imagine Standoff at night. That would be cool, the night map needs to be just that, an open map where you can see the sky very clearly.