Often the objects are painted or drawing upon to bring the work together in a unified design. In the nineteenth century children and other hobbiests cut out and glued cards, papers and other things to boards in the manner of a scrapbook. Since there were a lot of advertising, greeting cards, magazines and other materials available to collect, it was a popular pastime in Europe and America. In the twentieth century Cubists Picasso and Braque first glued newspapers and other papers to paintings and collage became an art form. Braque used a woodgrain patterned wallpaper piece in a still life and that method, known as papier colle, was also used by Picasso and Matisse.
All forms of art involve making creative decisions.
The art of collage involves the usual decisions of line and color, paint and technique, but it is essentially based on decisions of selection of material, choosing how to tear, cut or otherwise shape it, and where and how to apply it to the evolving design. Sometime particular text or images are used for their content and sometimes the materials are chosen for the color or other factors. Collage is not necessarily abstract or even recognized as collage at first view. Some artists build a collage of papers and other materials as the surface for a more traditional painting, or cut or shape materials in the manner of a mosaic so that the picture is dominant. Working with found papers and other materials forces the artist to concentrate on shape, line, texture, color and other design elements.