So I was thinking that since they added winter and a winter based enemies why not do all of the seasons and enemies for each. Why not take the scare crow idea and have them as things you can build and as enemies during fall. And perhaps a random spawn Halloween based monster. Even having wild growing pumpkins and pumpkin patches show up. Each pumpkin could have a chance of becoming some sort of plant based monster with a pumpkin for its head. Maybe the lower your sanity the more likely they are to spawn. A shadow or something could be seen flowing into it right before it rises up to attack. And during the spring there could b more bunnies and the king of the bunnymen could come out of a large wormhole or something of the sort.