Wondering if it would be possible to add support for river generation. Especially on continent maps.

Or mix and match content continents and archipelago for more diversity.

I spent quite a while thinking about rivers but never came up with any good ideas about how they would work. I am glad to hear there is some interest though....

Good suggestion about getting more diversity in the noise landforms. You should be able to get some good results by taking the Union of an archipelago and a continents pattern. It might be interesting to have a more sophisticated way to smoothly blend between different patterns, I'll think about that in the future.

Rivers should be shallow water and they could be generated by picking n (random between 0 and N, should favor low numbers) tiles in every new chunk as a spring. And then either make it flow downward if you have a elevation function or find the nearest water (not a spring or river) and do a random walk favoring the direction of the water. If the walk hits another river (not itself) stop there. There could also be a probability for rivers to stop.

One problem is that this would change existing chunks as the river is created. Most of the time this would be outside the players view and more importantly on land without buildings. But in case the river hits some building it has to stop there, or maybe a bit before that.