Place two or three thin throw pillows on the window sill. Prop one up on either end of the sill and one in the middle if there is room. Some window sills can act as additional seating in the room.
Choose a window covering that shows off the window sill. A valance or lace curtain works well. For heavy or longer curtains, install the curtain hooks high enough that when you tie back the curtains, you can see the design of the window sill.
Create a garden on the sill. Grow cacti, African violets or a peace lily. Choose containers of different sizes, textures and shapes to grow the plants in to add even more interest. Arrange the plants in the center of the sill or off to the side. Groupings of odd numbers typically look best.
Place a dried flower display or a single container of forced paper white or tulips in the center of the window sill. A single orchid off to the side also works well. A simple but beautiful centerpiece can give off an elegant feel.