Very pretty! I love the paint color you've chosen. How about Silhouette blinds with silk panels to match the walls?

Abstract art does not go with the style of that room ,maybe some white or blacked framed groupings ,this looks like a sweet little upstairs room. I think curtains all the way to the ceiling with grommets for easy open and close with bamboo romain shades over the window for privacy.

I'd order some samples first, but how about these?

http://www.halfpricedrapes.com/shoreline-textured-dupioni-silk-curtains-drapes.html

For the drapery rod, I would mount it so the top of the rod is the same height as the point where the adjacent wall starts to angle. That will create a nice continuous line around the room. If you have the budget, wall-to-wall draperies would be very nice. But, it would also be great to have the rod be just a bit larger than the window. At a minimum, I'd have the rod be at least 16" wider than your window. If you're using stationary draperies, I'd have each panel be at least 1.5 widths of fabric. Many ready-mades are just 1 width, but that might look skimpy on a window of this size.

It looks like you have a heating system running along the baseboard. You might want to stay away from a linen fabric or a linen-blend. In my experience the heat will cause the hem to shrink in the winter (but it does "grow" again in the summer).

My suggestion would be a knife-pleat or hobbled Roman Shade in a nice soft sheer fabric in a color to match the white in the room. This will make the window a very soft feature of the room, allowing a lot of beautiful natural light to come in the room. I would couple the shade with a nice ring top drapery in a fabric that speaks to you and complements the design of your room. I have attached a photo that, while different from your style, will show you what I mean.

Beautiful color choices. I would consider a white cornice just the width of the tallest middle section. It would anchor the wall and accent the beautiful breezy curtains. Height to place the cornice would be taste. Higher (like going to the top) will accent this architectural feature of the room and add drama and height. Midway between window and ceiling (if the cornice is solid on top) could serve for up lights or pictures. On either side of window would scream for beautiful tall vases or some type of white distressed tall wood accent lamps. For drama, you could add curtain drawbacks. Just some ideas to consider. Libby

Hi! Here are a few ideas for you:
http://deciture.com/shop/decor/world-market/natural-linen-grommet-top-curtain-54inx96in/ (these are natural linen-looking, and would go well with your current color scheme)

http://deciture.com/shop/decor/pier-1-imports/scallop-curtain-blue-gray/ (a little different)

http://deciture.com/shop/decor/world-market/birds-branch-burnout-curtain/ (these are white but I really think they would lighten up the space and allow natural light in if you wanted that)

Hope these help you!

this is actually the bedroom with the added ledge to give dimension and division . any input for window treatments would be appreciated.