Very nice shot. The "lone frog" works well for the card. I know it's hard to control these "living" shots, but it would have been nice to see a bit more of the frogs face.
i don't like the blur in the upper right corner or the half leaf on the left side, they are just distracting and take away from the beautiful capture of the frog. i like the subject and if cropped a little i could totally imagine this as a card.