I have wooden valences over the plantation shutters in my kitchen. They're held on by these cheap plastic clips that break off. In fact, all of my valences had been stacked up for 3 years in a corner of my dining room. Hours of searching local hardware stores and the Internet didn't yield any replacements. Luckily, I built a Reprap this summer. I don't even remember the laborious procedure I went through to get an STL, but basically, I started with a photo of the clip, used Photoshop to turn it into a high contrast image, then Inkscape to convert to DXF, and finally, OpenSCAD to extrude it.
Needless to say, this part made my wife extremely happy!