Here's a pack of blank greeting cards for the baby showers, birthdays, kids' special occasions. Handwritten cards are the sweetest. These come with envelopes and are 4"x4". One postage stamp is good for mailing them.
You could also frame them as tiny pieces of art as a collection, as they are reproductions of original abstract art. So many ideas!
All cards are printed locally in Austin, TX with non-toxic ink on archival paper.