Putting the bed on the 13' wall would work and could provide you with a sitting area. HOWEVER, if you plan to have a tv in your bedroom, generally those are placed on the wall opposite the bed and 18' would be a LONG way to have to see unless you have a large screen t.v. Have you considered NOT having double windows and doing two separate windows in each section. This is far from perfect but illustrates what having two windows could look like. I'd also increase the width of the front door, too, if possible, because it looks tiny compared to the double windows and large looming gable above it.

Check on an appraisers forum to see if there would be any difference in value. Unless you are getting cash for the sale or a large down payment from the buyer the appraisal will be the determining factor if you actually get more at the sale. If you do this change, do it for yourself and not for resale. If you do this change, make sure you don't make the current floorplan dysfunctional as that will take value away. If you are using the exact same square footage and not adding any, then it is doubtful that your home would add value but you would need to get twin sales in the area to see how much, if anything, is added to the value. It may open up the buyer pool and sell more quickly though. As the others mentioned consulting with a couple of Realtors in your area would help you get a handle on the current market.

Inspiration (except it needs to be a little more grown up since my boys are older)

I think shiplap has had its moment. So if you’re committed to one, I’d do headboard, but I agree with everdebz that less may be more. I’d start with the window wall and do nothing else.