When it comes to arched, angled, and odd-shaped windows there is no one simple answer. There are not a wide variety of options for these windows and the products that are available are limited in function and in size.
The arch or the half-circle is the most common shape that is placed directly above or as an extended part of a rectangular window. We cover a lot of these windows, especially in the hot summer months. If the window is in a second-story foyer the rectangular section can be made to raise and lower with a motorization feature. The arch would be stationary in most cases, however, there is an option to motorize as well.
Angled and oval windows present more of a challenge mostly due to the limited functionality. Soft treatments such as valances and draperies are a possibility, but that also would depend on how such treatments would fit with the décor of the space. Plantation shutters are most often recommended because they will operate efficiently and they are made from a template of the window, adding a beautiful, decorative element to the room.
Recently we encountered a poorly designed bank of windows in a master bedroom. There were 3 windows side-by-side with an arch above the center window. The windows were not installed properly and were not aligned. We made a valance with jabots to cover the entire window width and added stationary drapery panels on each end. The end result was a beautiful window treatment that covered the window flaws and added a soft, sophisticated design to the master bedroom.