When dressing bay windows - the function, and the size of your space should be considered.

In communal spaces where you want to see outside for full views, you may want to dress the head of the bay windows with a valance that covers the entire length of the windows. While bathrooms, or areas of privacy, plantation shutters that allow privacy could be used on the entire window, or only the lower portion.

Here is an idea book on Houzz that shows other ways to dress bay windows.

https://www.houzz.com/magazine/looking-at-beautiful-bay-windows-stsetivw-vs~11302