There are many ways to organize a Mixed Media abstract collage. One way is to repeat shapes such as circles, squares, triangles etc. The trick is to come up with different versions of circular shapes that don't scream "I am a circle". What you want to achieve is the essence of the shape which might include a sense of movement, direction, orientation etc. It takes awhile to learn how to "sink" a shape so that it does not look like it is sitting smack on top of a piece of work. You can paint over your "circle" or use only a partial "circle" or vary the sizes of your circular shapes.