A nice quick project to do with old paintings is paper weaving.
Fold an old painting in half lengthwise.
Cut slits along the crease leaving about a 1 1/2 inch border, and about an inch between each slit going down your paper.
Next you can either cut up another painting for your strips or use solid construction paper.
We used construction paper the same length as the paper and about inch wide.
Then teach the children how to weave over and under, making sure to alternate between each room.
Again, this is another one of those hand eye-coordination projects that is great to do with preschoolers.
It is also a fun way to re-visit a finished piece of artwork.