IDEAS

(what I'm trying to do with these is extend the continuing gameplay beyond the challenges)

1. Genetics
Children inherit either the hair/hair colour or clothes of one of their parents.

2. Villager swap
A way to swap villagers between villages. Maybe even trade them over the internet

3. Super villagers
These would be villagers that you trained to master in every skill (except parenting). They should live longer, or have some special powers or something.

4. Continued research
Research points should be needed for medicines or something, so that it was necessary to keep villagers researching even after you discovered everything

5. Continued building
Huts should perhaps actually decay, and need repairs, or your village size gets limited again (eg if they drop below 50% condition)

6. Watering the crop
This should have some kind of influence on either the speed of crop renewal, or the size of the crop. Currently it's a pointless waste of time. And annoying, because villagers get distracted from better things they could be doing.

7. Worshipping
This should involve some rewards. Perhaps villagers could have a Spirituality bar (rather than the Parenting bar, which I find kind of pointless, given that you can just keep dropping absolute amateurs together until they breed). Spirituality could affect health, longevity, the chance of having triplets or something. Cool things.

8. Regular tournaments
There could be a new tournament on the Leaderboard every week or month: eg for the most amount of twins born, or mushrooms picked, or Research points. Some kind of challenge to keep the sense of competition going, that also enabled newer players to compete with older ones (so it wouldn't matter if you had already picked 1,000 mushrooms, only the ones you picked for that week would count).

9. Downloadable events/puzzles/features
If this were possible to extend the game, it would be great. Even if you had to pay for them (a dollar or so, like extra skins for a game). So you might pay a dollar and your villagers could puzzle out how to build the Fountain of Youth. This would perhaps extend villagers' lives. Or they might figure out how to plant the Garden of Love, which would increase twin births. Or the Mystical Observatory, which would increase research rates and add some really cool celestial-themed Special Events. Etc.

10. Reward villagers
People winning tournaments, or from other lucky things, could have special villagers born. Like the Golden Child. They would wear special clothes and have special looks and powers.