I was looking at this post from Acorn Pies and was reminded of a craft my daughter and I did a few Easters ago. We cut a cross of foam board, painted it black and then used crushed Easter eggshells to create a mosaic. Well, craft pack-rat that I am, I still have a ziplock baggie of shells from years-gone-by, and I found a cute wooden box which I had already conveniently painted black, so I was ready for this one.
Start by saving your eggshells. When you peel them, remove as much of the membrane as you can. Then let them dry thoroughly. Now, assemble the following: eggshells, white glue, toothpick or skewer, white chalk pencil (or light dressmaker's pencil), object to decorate, Modge Podge and a foam brush with which to apply it.
Take your object to be decorated--it can be any color, but I just happen to love the way the mosaic looks against black--and trace out a simple design with a white chalk pencil or whatever works.
Now fill in a portion of your design with the glue. Don't over-do it. Take a piece of eggshell and lay it in the glue, then press gently but firmly with the toothpick to break it. Use the toothpick to move and separate the little pieces and expose some of the background color. When you have completely filled in the first portion, apply glue to another and complete your design.
When the glue is completely dry, seal with a coat of Modge Podge--or several, if you want to sink the design below the surface. A final coat of clear, high gloss acrylic is a good idea, but not necessary.
If you have another idea for something nice to do with eggshells, let me know!