Something that I've talked about with many different players that we all seem to like the thought of is more types of leaderboards.
For many people here, reaching the top of the leaderboard is a major goal and incentive to play. I think that we should have more of them for people to climb. Things like:
Greatest Explorer - Kingdom who has explored the most land
War Monger - Kingdom with most castles won in battle
Reaper of Souls - Kingdom with most units killed in battle by resources
Master Magician - Kingdom who has used the most amount of wizards
The Economist - Kingdom who has produced the most resources (wood/iron)
The Treasurer - Kingdom who had produced the most gold
I'd love to hear all of your suggestions as well. But with these alternative leaderboards, people will have other things to strive towards.