For about ten years now I have collected pictures to use as ideas for new pictures.* I often start a painting by gathering a small pile of image sources, either intuitively, because they seem to go together, or for a specific purpose. I used to create a pencil-and-paper sketch of these various sources, attempting to synthesize them visually before starting the painting. I would also scan them, resize them, struggle through PhotoShop layers to get them to fit together just right. At some point I thought, "what I really want is this head on that body," and went: rip, slap, tape, done. I realized that the collage is visual shorthand for my pictorial plan. It didn't have to make sense compositionally; the collage is a convenient way for me to gather a group of visual sources onto a single page. Plus, the faster I make the collage, the more unexpected and interesting visual moments show up in the result.
I've scanned a bunch of these collages and uploaded them to this Flickr set. Enjoy.
*Old-school illustrators call this a swipe file. Though it was years before I learned that what I was doing was a traditional practice; before then I thought I was (gasp) stealing and that it was (gasp) wrong. Thank you, illustration.