Outlining the edge of the map or printing on the entire screen, so that players can distinguish between the different game options, SO players can see (at a glance) what type (trench, nuke etc.) of game that they are engaged in.
Nothing like doing your turn only to realize (later) that it is not a standard game.
Example: Entering the game, I see a transparent NUKE or TRENCH Flashing in front (the entire screen) of me, before I press begin turn.