I think I saw lakes/ponds in some parts of the videos, but I wanted to write this anyway 🙂
Addition to biome generation of rivers and lakes. Lakes could maybe be added in the last 1-2 stages of biome generation so they don't become too big, maybe a small random chance to spawn water in a landlocked area, and treat small areas of water as lakes rather than oceans (so less chance of sandy beaches)
Rivers could have sources and mouths selected at the end of the biome generation process. The source could be high up, with the mouth being at the nearest ocean. The rivers could actively go downhill, potentially even going down cliffs creating natural waterfalls. The rivers could get larger when they are close to the mouth.