Go google shopping. The spot between the curtains needs nothing. Think a bit larger, or a group of three related. We don't even know the size of the wall : )

The space between the windows in pic #3 is not blank. It’s absolutely fine. The space near the kitchen counter in pic #1 might need something, or it might not. The pic is narrowed in too close for us to tell. What’s to the left?

Pic #2 is the only one I would worry about. A big piece of artwork. I mean BIG like measured in feet, not inches. Maybe a suble watercolor? The existing blue piece on the other wall is lost behind the light fixture.

Nothing between windows and suggest waiting until you replace the dining set, as it’s important to work with/complement its style.