This The Wiggles icing image is approximately 16.5cm. Completely edible.
To place on buttercream:
Cover your cake with buttercream and smooth. Carefully remove image from backing (place in freezer for 5 mins if needed to help with removal), then place on top and press down.
To place on fondant:Cover your cake with fondant. Using a slightly damp brush, dampen the area the image will sit on, or alternatively, use piping gel. Remove image from backing as above and press and smooth.
Photo is indicative only - printing with edible inks is duller than regular photos.