Could you post either a picture or a layout - even somthing hand drawn to give others a perspective of the room? Thanks. You'll get more assistance if folks have a good understanding of the layout.

If I'm picturing it correctly I think you are on the right track with your canopy idea. A full canopy can be very girly though so see the pic below (if I do it right!) for an idea that could work. A strip canopy at both the head and the foot of the bed, or whereever the door is that needs covering, could work for you. Depending on your wall colours doing your bedding in grey tones can have a masculine feel but still be softened by the sheers of the canopy. Slate greys, metal greys and soft greys can go beautifully together in a bedroom. Go chocolates and browns if you like a warmer look. If it needs to look more feminine throw in some ruffled/textured cushions and accesories in a soft pink or blue but if it needs to look more masculine throw in cushions and accesories in a bold/strong colour (red or black) with straight clean lines.

Here's an example of bedding that could be softened with a white sheer canopy yet maintain a masculine look. Also, the ruffled cushion could be used to soften if needed. I made this one out of baby wipes..

You can create a more masculine-looking "canopy" with paint: using simple trim (painted the color of the rest of your trim) extending from the lower wall the width of the bed up the wall and out from the ceiling, mirroring the bed onto the ceiling. Then paint the entire interior of the wall above the bed (including the door) and ceiling a different darker color that coordinates with the room. You can then hang a picture/canvas/map or even a suzani fabric hanging to cover the door itself. Even if you don't hang anything to specifically cover all edges of the door the paint will cause it to camouflage quite nicely. This is a nice effect that will make your ceiling feel higher (nice in a narrow room) and gives a romantic feeling in a little more masculine way. You can also hang a cool chandelier from the middle or at the end of the bed.