In the kitchen, I would paint the window niches one of the medium toned colors from the granite. If you had tile, it probably would have been installed right up to the ceiling which is why the space looks off. If you paint and it still looks unfinished to you, I would add a modern valance. Many people here like Roman shades but imo they are difficult to hang in way that makes them stay neat and even.

In your bath, an inside mount natural fiber blind or shade would look nice.

Paint in the kitchen is a good idea.