How about put something white behind the masonite so that it looks a window treatment looking in from the outside?

We have done this twice in two different homes. In our case it looked like drawn window shades.

We put up some cardboard on the window to the right and white paper on the window to the left to get an idea. I think the white draws your attention to the window more than the brown. The masonite is a little darker than the cardboard so we're going to cut some masonite to fit the window and take another look. I'll post another pic once we do that. We decided that later, we could always frame in the section of the windows outside that we're closing up, stucco and paint.

You can play around with colors. Maybe a light beige.

eld6161, you said you've done this before. What materials did you use?

We were thinking we could paint the Masonite whatever color we decide, but with what kind of paint? Should we paint on the rough or smooth side? Obviously, if we painted on the smooth side, we'd need to sand and prime it, right? Could we use a paint with primer in it already?

Our window were the typical glass pane. My husband sprayed them white so from the outside they look like shades.

Yours are obviously different and you only want to do half.

Looking at your examples I think neither choice is ideal.

Since you do have other natural light, I personal would close them both in.

For me, glass block is not particularly pretty. Added to having half of one window on that wall.

I know people like to save windows at whatever cost. One of ours was a bathroom that we added using space from the back of our garage. We couldn’t keep the window and have an efficient layout. This was an extra bathroom for our oldest daughter. She absolutely loved it not having a window!

i just spoke with a glass block specialist who doesn't recommend putting anything between the block glass and the shower wall due to potential moisture build up between the materials. So we just came up with another idea. We could keep the windows as they are in the shower and put sunscreens on the outside (to match the rest of the house) for the privacy. That may be the best option.

Please post whatever you decide. I know I would like to see what you do!

eld6161, my husband said it will be sealed up fine so we're going to continue with the Masonite after all. I bought Zinsser Bullseye 1-2-3 Primer and DE exterior paint. We'll sand the Masonite, prime and paint it. Eventually, we may frame in and stucco these on the outside anyway. But in the meantime, we'll add the sunscreens. I'll post pictures when they're finished.

Eld6161, shower is finished and we're so glad we closed up the windows. Sunscreens won't be added after all, but we think the windows look just fine from the outside. Shower looks better inside without the windows. See the little visitor on the window ledge? :)

The white color looks way better for the windows. Brown is not in and out dated.

White was drawing attention to the windows. This color blends nicely with the house and makes the windows "disappear." We think it was the best choice.