I have been collecting these for a couple of years. Most of them are made of wood, but a few are styrofoam. I have been looking for interesting ways to use them without damaging them.
I saw the idea for a peg rack made of thread spools somewhere, but the designer used wood screws and screwed directly into the spools! Horrors! I spent some time finding the right arrangement for the spools, as they come in lots of different sizes. It worked out well that some of the shorter ones got stacked atop two peices of wood, the taller ones I situated below on the single layer of wood.
Once I had my layout configured I prepared the wood to attach the spools to it.
This paddle bit did a great job of removing wood from the screw hole so that the finished piece will lay flush against the wall.
Here you can see how the back looks with the hardware installed.
Now all that is left for me to do is attach this to the wall. I had to use tiny washers on some of the spools but most I did not as I wanted to preserve as much of the visual continuity of the spools as possible. I may disassemble this and patina the screw heads at some point.