Cut various-sizes of circles, triangles, squares, rectangles, ovals, trapezoids, hearts, stars and ther shapes on colored paper or craft foam. You can use craft punches to make tiny shapes.
Instead of making your own shapes, you can buy a bag of foam shapes or paper shapes.
When you're done playing and coming up with lots of images, decide which ones you want to put on your picture. Glue the shapes onto the background paper.
This winter picture with a cute snowman and lots of pine trees is made up mostly of circles and triangles. A few rectangles, ovals and a trapezoid, complete the picture.