What better way to get some use out of old catalogs than to use them for references for drawings? Gather up as many catalogs as you can, they can be clothing, home furnishings, and/or anything you can find. If you don't have a source of catalogs you can use magazines or books with images in them.
Use as many different images as you can. This collage does not have to be symbolic or meaningful, just fun and a great way to practice drawing all different shapes/things.
For my collage I worked on an 11" x 14" sheet of bristol paper, so I knew I would need enough drawings to fill the entire piece of paper with a couple extra for discarding.
I began by drawing all sizes of images, working quickly and not getting caught up in the idea of perfection. I then collected all my drawn images and cut them out. I then placed them on the bristol paper and glued them down. I then brought in a layer of gouache to add some color. Feel free to take this exercise and stretch it out any way you can!