We are not window treatment people either, but have started to add some as we've reno'd/decorated a few of the rooms in our house; two bathrooms and our office. They really do help to finish off a room. That said, we're not covering our kitchen bow window, or the DR bow window, though I might consider something for the DR window at some point--just for the window panes themselves, not to cover the whole bow-unit. We used Hunter Douglas' Designer Screen Shades in the Roman Shade style (ours are mounted inside the frames becuase of our window style/frame depth). The shades are very clean-lined and range in sheerness. With the sheerer weaves/fabrics, you can see outside with them down and they allow a lot of light in.

Beautiful space!! I love, LOVE your banquette seating!! Congrats on your remodel and welcome to the forums here! Okay, here's my thinking with your window treatments. I love natural light. If you need privacy but want to let the most light in as you can, I would use a light-weight or sheer fabric that would give you the privacy and yet allow the light to filter through. If you're looking for insulation from the cold, then you can't do the light-weight fabric. You'd have to line the curtains/shade with a thermal lining, which would block out your light. And if you're using a roman shade, I don't know how effective it would be as an insulator unless you left it "down" all the time. I would think about doing plantation shutters? Easy light control, excellent privacy, and they also provide insulation. (We just installed some in MBR and really feel a difference in temperature). I think the planation shutters would look nice in your space. You have a lot of beautiful elements in the room and I think the shutters would complement your decor.

I would do everything to the room first and then think about window treatments. The clean no curtain window could work here especially if privacy is not a concern. The side chairs would be nice upholstered in an accent color to add warmth and softness. The mantel is a bit low so I would fill the wall mantel top to ceiling with a mirror or large painting...leave the sofa as is, they are nice I think and add pillows in your accent colors.... Toile chairs would be fun! Example of large mirror and large greenery over the mantel

Have you already purchased both the rug and sofa? They work fine together, and the rug provides a nice color palette for you to use. If you want to lighten up the room, use off-white linen curtain panels, mounted on black iron rods and rings. Blue chairs would work well, but not too dark, a light to medium color, in a textured fabric. Maybe velvet or chenille, with a subtle weave, like a herringbone or chevron.