There aren't really any walls between your windows. That is trim and and trim is most often painted in a gloss or semi-gloss white (family) color. My preference is a crisp bright white. So, IMO you are not making a mistake. The mistake I see is the ceiling treatment in your window bay. It's distracting and doesn't compliment. Rather it takes away from the serene quality that the bay and the room should have. Unless it's needed for privacy I wouldn't recommend any window treatments either. Good Luck!

I agree and the window is already a feature no reason to do anything else to that wall but that wood trim needs to go.