Build it for you, not for the choices of some unknown, possible future buyer. I doubt a few inches are going to make much of a difference in sales down the road.

With drapes behind a king headboard and/or an iron headboard would soften the look in front of a window.

King wood headboard:

These slope down on the sides

https://stylebyemilyhenderson.com/ask-audience-master-bed-front-window

Do YOU want to sleep in a queen bed? Most couples don't.

Show the room in a DRAWING or your floor plan. With all windows, solid walls , openings to wherever noted INDIVIDUALLY.

12 x 12 is not the whole story, nobody is in there but you. Show and tell time. Full context please?Thank you! Even graph paper is fine. Two 1/4 inch boxes, to ONE foot.

"Random" means transom, and "near the entry" entry.....and show it all? thank you.

Once done that may not be where you really want the bed. The space that a king would take up into the window can be softened with drapery so leave it as is. Not worth the expense and overthinking it and causing possible work order changes which are very very costly.

12 x 12 isn't that big of a bedroom; a king is going to be cramped in there, doubly so if you plan to add a dresser or some other furniture. Is this your main bedroom, or a spare?

Stick with the bed size you prefer. The room will accommodate either bed size. The windows can be dressed for the space. Besides, you might want to rotate the bed to the other wall at some point.

Why all those skylights in a bedroom? I like to sleep in a dark room, so those would be more of a problem!

Sorry you are building and already worried about some invisable buyer why???? wht was thw reason for that window placemant when you were designing that space .IMO a 12x12 bedroom is small for a king bed anyway so stop stressing get the queen you love and carry on. I do agree the wall with the high windows seems more fitting for a bed. BTW we have been married for over 60 yrs and went for double to queen and have never needed a king bed

I might be important to show a potential buyer that the room can fit a king bed, but this would be done during staging and at the advice of your Realtor.

We prefer a King but we are two big guys.

You're overthinking it. jackowskib has the best advice. Get the bed YOU want and forget about resale!

A California King is narrower but longer so that would be a good option. I think it's what we have.

Did you build to FLIP? : )

Are you building this house for yourself? If so, make the bedroom work for you. Whoever buys it “in the future” doesn’t matter right now.

If you’re building it for prospective buyers, I would make the room larger if it’s the Master.

If you are concerned for a King vs Queen, I would probably install "skinnier" windows rather than block them off or install another transom like the other wall. If the already transomed wall is next to the entry door, then that is not an optimal place for a bed to go (you see the head pillow from the adjacent room and vice versa).

But thinking more, there is the main double window, the bed flanking windows, the double transoms, and 4 skylights in this 12x12 bedroom? Does the door swing conflict with the transom? Will there be a dresser under the transom right into the entry circulation?

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What is troublesome in these pictures is that there are no structural rafter ties. When you have a cathedral roof without a ridge beam (you have a ridge board), the rafters push out your walls and the ridgeline sags in the middle. I assume there is no structural engineer here, and a framer thought that putting 3 boards across the roof at midpoint of rafters would do the trick, but they are neither rafter ties nor collar ties. They also, if you plan to encase them, dead end into the edge of the skylights which is unnatural looking. If however, you plan on a flat ceiling and haven't installed all of them yet, the above information still applies.

Also, if your skylights are within 3' of the trimmer rafter bearing, they should be doubled trimmers.

Another option I like is to fill the wall with a "headboard" from corner to corner with a shallow top that can be used as a shelf at 1/3 the height from floor to ceiling. Any size bed fits nicely. I'd be more concerned with the appearance of the home exterior and whether the windows look good and are proportional from the outside. I assume they currently do.

Sorry I couldn't attach this to my first comment. I had to go hunting for an example.