Help finishing my DnD setting map

[Chashio]

Not that I'm more experienced... but here's what I'd do, basically. Started with your major snow caps on the mountains (aside from direct rain and ground springs, snow melt adds a lot of water to river systems) and tried to follow the contours of what looks like low spots on your map. And a lake/pond/bog where there seemed to be a depression. And it's not perfect, obviously. But as for rain, prevailing winds will have a say in which side of the mountain range is most wet. Depending on how tall your mountains are, they might be pretty similar (tall mountains catch rain water and create a 'rain shadow' on the far side, so it's drier). But nit-picky little details aside (sounded like you wanted them), Sera-H has it; start from the mountains and go downhill.



And if you can't open the psd file...