I'm no designer, but seeing as no one else has chimed in, I would go inside mount light blocking. Don't ask me about color or style, though.

I like my first idea best as far as use of space. I know people say not to put toilets on an outside wall. We had one in our last house in Iowa, but we had 2X6 construction. I don't know how high your window is, but I'm guessing the toilet would fit under there. The shower would be 5 feet long or shorter if you want a wider space to get to the toilet. (kind of tight the way I have drawn). You could do a 5 and half foot long shower and do an angled door at the left end to allow room between the shower and toilet. The vanity would be about 7 feet long, unless you do a 60 inch vanity with a linen cabinet at the door. I would reverse entry door swing if you do that.. The second top right could work and you would still have a small closet. The bottom left plan would require waterproofing your front window. Hopefully someone will give you other ideas. The bottom right plan is bigger, but no closet. Each square equals 1 foot.

I would do top-down/bottom-up shades. You'll keep the look simple and you'll be able to lower the top half to see the night sky. They are also available with room darkening fabrics.

thank you! I hadn't considered gray for the rug. I know it's neutral but wasn't sure about adding another prominent color. I had been looking at blue (navy) or red, but wasn't sure if I could pull off a geometric or striped pattern with the stripes on the one wall and the busy coverlet pattern. Would anything like this work: https://www.wayfair.com/rugs/pdp/highland-dunes-jago-striped-handmade-tufted-ivoryblue-area-rug-hidn7327.html?piid=31943158 https://www.overstock.com/Home-Garden/Safavieh-Handmade-Childrens-Stripes-New-Zealand-Wool-Rug-8-X-10/7026050/product.html?kwds=safavieh kids rug&refccid=ULYBSLO26RNZEJ2EJNF43JVRCY&rfmt=&searchidx=40 https://rugs.com/navy-blue-5x8-angelica-area-rug-6254554?gclid=CjwKCAiAo5qABhBdEiwAOtGmbuh7jyBd8WHXU0Cy4nxOr8FmnfQYeKgen_8cOg94j-35Lq0Xpk_VKRoC3H0QAvD_BwE&gclsrc=aw.ds https://rugs.com/red-5x8-lattice-frieze-area-rug-6293322?gclid=CjwKCAiAo5qABhBdEiwAOtGmbtT_VU-HM4GTX9IUynY-fVTzqNCAM2Sj-OIGPmKMEXcocrfrWtQRphoC0UgQAvD_BwE&gclsrc=aw.ds https://www.wayfair.com/rugs/pdp/breakwater-bay-edgebrooke-red-rug-w001802626.html?piid=2007201777 https://rugs.com/red-6x9-kasbah-trellis-area-rug-6295252 Or is there another pattern/color I should consider? thank you!!