The composition here is created from a layered stamp and some Photoshop tricks. The basic image is made up of two stamps. The top layer is carved from a picture of a flower I found online from an old book illustration. The bottom layer is a mostly solid shape of the flower with some slits cut in it which let you see the white background. If you stamp the bottom stamp in a light color, and then the detailed flower image on top, the result looks like the blue flower on top. I created the others in Photoshop while playing around a bit. I used the shape from the solid flower to crop some photos of flowers, and then layered the detailed black stamp on top. You could get a similar effect from a real stamp by coloring the solid flower in multiple colors with markers.
I fun resource which I used for the photos is morgueFile. While the images are not in the public domain, you can use them for anything other than directly copying them as they are. So they are great starting points for collages, art projects, and derivative designs.
Each layer of the stamp, and the three layered images are available in the gallery.