feline fanatic

Traditonal attic window is only framed on two sides. Either the right or left and the bottom. I always think the 3-D effect of the window pops when you use the dark on the bottom and the light on the side but it works both ways. Here is a picture of mine so you can see what I mean about only two sides being framed, this one I actually used the light on the bottom and dark on the side to give the illusion of the light coming from the top. While this is not a panel but several window blocks you get the idea and framing only two sides gives more of an affect of looking through a window. Maybe your could use a narrow plain fabric for the other two sides in a dark neutral color?
To get the angled corner which is necessary for the 3D effect you can do a set in Y seam like I did or simply do a HST block in the corner. Prints usually hide those seams nicely.