It looks as if you could add one side lite in the space with the door; I would do it in frosted glass for privacy. See attached photo...

How do you decorate your place, what kind of style, colors, and feelings? That will greatly influence the type of door you might want. Also, think of your budget, and whether you want to install it yourself or hire a professional (you don't need to tell us, just keep that in mind). Then look around Houzz, in the products page, they have lots of interior sliding doors and hinged ones, from elegant frosted glass in a dark wood frame, to rustic reclaimed wood planks. You may not want to purchase that exact model, but it might give you a better idea of what would fulfill your airflow needs without sacrificing style.

I agree with painting the doors. All my interior doors are a deep charcoal grey. You'd be surprised how expensive it makes them look. That aside I would start with a rug. A huge rug. Something chic with a lot of color. Then add love seats in white, colorful pillows, and chairs in fabrics that pickup the colors in your rug. No BIG furniture. Just because you have a big room doesn't mean you need to stick a brown sectional in it. A couple fancy topiary would look great under those windows. And dont forget lighting.

Hi Cynthia, thanks for your comment. I still haven't decided about lighting. First, I'm trying to get as much natural light as possible. If there are still some dark corners left, then I'm planing to use light on those areas.