My wife really likes the bathroom doors, but was quick and clear to state that she didn't want light coming through the bedroom door! Oh. I was literally back at the drawing board.
So I worked up an idea I had been thinking about as a variation on glass doors. Using 3mm (1/8") thick birch plywood with the traditional zinc channels (called "cames" in the stained glass industry) used for leaded glass, I could make a panel to insert into the door that was opaque and had many options for design. The final design included copper and zinc cames along with an opaque black glass with the stained and varnished wood.
The solid black glass is a nice contrast to the wood, adding a glossy surface to reflect light (even some green from the gardens!). The copper has a warm tome that will darken with age, adding more contrast between the different metals.
Traditionally constructed stained glass doors (or with clear or beveled glass) often used zinc cames. I have repaired some that were 75 years or more old, as the solder joints get fatigued over years of use and then crack, making a weak spot in the panel. One factor for that is the weight of the glass itself flexes the door panel as it is swung closed. Rather than try to make a really rigid door panel, experience has lead to allowing the door to flex a little, which avoids breaking the glass if the door is closed abruptly. If broken solder joints allow too much flex, then the glass can break - which is usually why I have been repairing them.
This door, being made mostly with a thin wood, is very light and will flex less than a similar design made with all glass. This should allow it to remain intact for many years of use.
And it definitely stops the light from getting through..