While my phone will not let me format right now, I have a suggestion that could bring in more nations. This may have appeared before in different incarcerations, but here it goes.
UNLOCKABLE WONDERS/IMPROVEMENTS
How will this work? Rather then offer a prize to the top runners, this would unlock a reward wonder or improvement for a certain amount played. Players can link their SE and TE accounts and the Game will time your length of play. The longer and more rounds a user plays, the more chance they have at unlocking the wonder/improvement.
For Example-
1 Full Round played = 1 Reward Slot opened
1 Half Round Played = 1/2 Reward Slot opened
6 Rounds Played = Reward Unlock
So on and so forth. This is still a WIP, but I was hoping others have ideas to build on this idea.