Clean both sides of the window glass with glass cleaner and paper towels. Let the window dry completely.
Decide which side of the window should be the front, and place the window on a flat work surface with the front side facing down.
Trim around the edge of each photo with scissors to refine the shape or make the photo fit the window.
Pour Mod Podge onto a paper plate. Use a foam brush to apply a thin layer of Mod Podge to one of the window panes.
Position the photo on top of the wet Mod Podge with the right side facing down. Add more Mod Podge to the brush and cover the back of the photo entirely to secure the photo in place. Lift the window and check the front to be sure the photo is completely adhered.
Repeat the process for each photo and window pane, then let the window dry for at least 24 hours before hanging to display.