Draw a simple picture on the cardboard. The picture should look something like the pictures you see in coloring books, with bold lines and spaces to fill in.
Fill in the spaces with seeds. Experiment with different sizes and colors all over the picture.
When the seeds look like they are in the right places, glue them down one at a time. Fill in any gaps with a line of glue and poppy seeds. Allow the picture to dry completely before hanging.