Form, function, and style are keywords that come to mind when considering how to dress windows. As a design professional, I look for challenges in a room to guide me.
For example; in a small dining room with two single windows on the same wall, I would consider an asymmetrical design with a mirror image to keep the window treatments from over powering the room. Panels on the outside of the two windows with a valance and jabot meeting toward the center would make the room appear larger than it actually is.
This application balances the two windows, allows more light to come in, and provides a more dramatic, pleasing look for a small dining room.