For the bee postcard I found a bee picture via Google Images. I printed it out, placed it over the cardboard and poked along the lines with a thumbtack. Then I played a little connect the dots with embroidery floss. With the sewing machine I stitched another piece of cardboard to the back for a place to write.
For the flower postcard I Mod Podged on some pre-cut paper flowers and glued down some plastic jewels for the centers. With the sewing machine I stitched another piece of cardboard to the back for a place to write.
For the frog postcard, I traced on a frog on to a piece of balsa wood, and drew the stages of a frogs life cycle. I used tiny google-eyes for the egg stage and dressed up the adult frog with some green google-eyes and sequins. I did a couple of coats of Mod Podge over the entire thing to strengthen the wood and glued on a piece of card stock to the back for extra durability and a place to write.