The topic says it all. But to clarify, we would like to sit on the side of the train that has the best view.
[Edited] From driving in that region years ago, I remember forming the opinion that it was mostly a bunch of trees. You also pass a couple of big lakes and lots of small ones. Between Kristineham and Karlstad, the largest lake is to the south (left side) of the tracks. If the train's not full, you can switch seats when you like.