Can I put dried fruit or nuts in the night before?

I would definitely put dried fruits and nuts into the overnight oats the night before!

If adding dried fruit, I'd add a few extra tablespoons of liquid, as the fruit will absorb some of the liquid. The flavors of the fruit will blend with the other flavors, making it even more delicious.

The only caveat I'd make is this: if you put nuts in, they will soften a bit. If you like them that way, fine. If you prefer them crispy, wait to add them until right before serving. ;o)