I had colorful, showy curtains all picked out, but then after the walls and trim got painted, I decided I liked the clean, simple look of the windows with nothing on them. Sorry I wasted so much time and energy on those first curtains, because they are not going up.
I had some muslin in my fabric stash and made simple roll-up shades for the windows instead. I had all the materials, so I just had to go buy two tension rods ($5 each) and I was set!
I used some of my vintage lace around the bottom for a hint of color, and some vintage trim as ties for when the shades are rolled up.
I love how tidy and simple it turned out. I might be turning into a minimalist in my old age. :)