Here is a valance I am not wild about.
I almost think it is that solid piece of red in the center. I'd probably like it better if they had used the same fabric as the gathered side pieces. It also could be that in this photo, anyway, the colors in the valance don't relate to the color of the tile.
If you have a flat valance or cornice that you'd like to change, you can see how easy it would be to add the side pieces.
My favorite version of this valance is when the center flat section is curved upward at the hemline.