Pops of color, design, patterns. I like the black and white patterned ones because they evoke Neuzz' mural patterns (Beautifully silkscreened plywood tiles are outfitted with a magnetic backing that allows for easy, nonpermanent installation on walls)
Make unique dip-dyed curtains. First, dip the curtains into in a container of water and let the water go up a bit higher than where you want the topmost part of the dye. Then take them out and mix up cold-water dye in the same container. Finally, dip the curtains back in, to 15cm below where your waterline is. Once the fabric is dyed, hang the curtains up to dry, then sew on a pompom trim to finish.