I would leave it square. Half round windows require custom shades

Personally, I like it. or a triangular window. I did front gables with some form of arch under it. I did my back window to match gable pitch (on right of pic).

No

definitely no

I would not.

Particularly if you need light control in a bedroom they also make window treatments on the inside more complicated.

(at least no shutters on the large window, where they look silly)

I wouldn't. Looks a bit misplaced with the style of the house, IMO.

Thank you for your opinions. My concern is that the room will have a cathedral ceiling and was trying to make the window larger but I m most co Verne’s about the exterior look. This is a 1940’s colonial red brick on the bottom and the existing siding is white but would like to give it a fresher look, also the roof is reddish too.

I like the half moon in your design. If it were me, I would not bother with a window covering for it. There’s a large Palladian above the windows in our master bedroom, and we just put a Roman shade on the rectangular part below and left the top for a glimpse of the stars. I love mine and think you might enjoy it too.

If you want a transom above that window, try a segment head transom.

It's called that because it's a segment of a circle. You can make the legs as long or as short as you want.

DO NOT USE a half-moon window! It's a leftover from the 90's and will instantly date your house. The elliptical transom you've got pictured needs to go on another, more traditional-style house.

Your drawing shows an "arch top" window, not a "half moon" window. I would not use it there at all. Maybe a round louver (even fake) in the gable.

The 'half moon' (as you describe it) window is completely inappropriate for your home. Yes it dates it right to the 1990's - and not in a good way. I would do a rectangular transom window, properly installed, if you are looking for more light.

Also, as promised by others above, remove the shutters on the double windows. The windows are too large and your shutters too small to look functional.

https://www.lifeofanarchitect.com/residential-architecture-101-shutters/

Take the time to study windows, doors, shutters and a little bit of architecture before you add this master bedroom addition. Ask your architect questions.

http://www.oldhouseguy.com/

Look at the rectangular transom windows on the first floor of this home. So much nicer than the window shown on your sketch IMO

If you want to emphasize the volume of the space on the interior and provide interest to the gable add a rectangular window in the gable above the other windows. IE it will read as an attic window...

This house is fancier than yours and is just to convey the window idea

How about just using a longer window?

If your house is mid-century Colonial revival style it's possible that a palladian window with a true, stilted, semi-circular or one-centered arch window would not be out of place on your house somewhere, but these were either over the front door on a symmetrical house, or clearly on a stair landing between floors, not in an asymmetrical gable at one end.