Here is a fun craft you can do to use up dyed egg shells. It is appropriate for almost all ages.
I had some dyed (empty) eggs left over from an Easter project. This toddler had fun smashing the shells.
Then he began to glue pieces of shell onto construction paper. An older child may wish to create a mosaic picture.
The toddler enjoyed placing the pieces of shell where he wanted.
He liked the crunchy sound the shell made when he pushed down on it.
He got to see what it feels like to have sticky glue on your hands. He wasn't sure he liked that sensation, but we told him it was okay, and that we could wash it off later.
He liked squeezing the glue the most, and grimaced like a weight-lifter when he did it.
Try not to direct your child too much when he is creating art. It is not the result which matters to the young child, it is the experience. Making art engages several senses at once: sight, hearing, smell, and touch. That is very important to your child, and much more important than making a recognizable product.
But I am probably preaching to the choir, right?