If you have a fabric that has his favorite things on it==fishing, hunting, reading, carpentry etc.
You could make an attic window by fussing cutting the above fabric for the window and using complimentary fabrics for the sides.
If the fabric is a big print or has a scene that is fairly big, cut the fabric scene into fourths and use these as the panes, and use coordinating fabrics for the frames. The overall look is of a paned window showing the scene outside. Sounds mor difficult than it is.
Good Luck.