I prefer to have the windows themselves and the incoming sunlight stand out more than my choice of fabric. (If it were practical, I'd just leave my windows bare.) For rooms that don't get a lot of light, the white is bright on its own. If you want something more adjustable, blinds and roman shades made of natural materials add texture and a little color without competing with their surroundings.
Images: 1. Design*Sponge 2. Liz Fabry for Apartment Therapy 3. House Beautiful 4. Western Interiors via Odi et Amo 5. Casa Sugar 6. Design*Sponge 7. Leah Moss for Apartment Therapy 8. Freunde von Freunden 9. House to Home 10. West Elm