I think a night time feature would be cool. Have it set to the time zone of the player defending. Day time attacks would be just like now, but night time attacks would work a little different. Archer tower ranges wouldn't be as good unless you have torches out to light the surrounding areas. Likewise, attackers would not see as well and might not always attack in the same way you are used to. Defenses could also include traps that are visible during the day, and attacking troops would avoid them, but at night, would run straight in to them.
Also, new troops could be introduced that do better at night than during the day. Something that runs around with a little light source to help attackers find their way and avoid traps.
