I just got to play Backwash for the first time on MCC, and I loved it. While the game itself, a a nice multi-flag CTF, was fun, the dark eerie atmosphere of the map sold me. The dense fog and forest made for exciting gameplay, and standing on the hill by my base shooting enemies through the fog to cover my flag carrier was a cool experience. While I can see competitive players not liking the vision difficulties with the fog, I think maps with a similar dark or foggy environment would be fun for Halo 5.