Hiding the Doors
Consider adding a curtain over the door. Curtains can be attached via rods at the top and the bottom of the doors, but use a loose-weave fabric, one that will allow the air to flow through. Consider using lace. Or if the door is to a closet and the room is spacious enough, consider a standing screen. Perhaps a black, lacquered screen would fit the room's decor, a carved wooden one or a more modern, metal screen. There are even screens made to hold photographs if such a display would add to the room's appearance.
Beautifying the Doors
Perhaps the doors simply need to be sanded down and re-stained a more suitable color. Or paint them, making them whatever color would enhance the room's design. If you are artistic, you could paint designs (something as simple as lines or flowers) or an image across the louvers to make them more appealing.
Decorating the Doors
Decorate the doors to give them personality. Weave the ribbon in and out through the slats, attaching them to the inside of the door with a staple gun. Or perhaps use ribbons the same width as the louvered slats and glue the ribbons horizontally across each slat, covering the wood with fabric. Consider a color pattern that is meaningful, such as your school colors. Or decorate the doors by weaving thin floral, silk garlands through the slats along the edges, framing the door.