Dishfunctional Designs: Upcycled: Neat Projects Made With Old Photo Slides - I wouldn't convert all the slides to digital and then make curtains like some of these designs (slides last longer than digital!) but surely there are some duds to play with.
Window Cover Using Old Picture Slides, + 49 other recycling/upcycling ideas. This may be a good use for those old commercial slides sold to tourists that I found among my grandmother& photographs. Surely better than throwing them away, as she suggested.