There’s a whole world of forums/boards for graphic artists, where they swap and critique art, most commonly with Adobe Photoshop images, Macromedia Flash animations, or 3D stills or animations from Alias Maya or Discreet 3ds Max.
In a lot of cases, the art is collaborative or competitive. The biggest genre for this is Photoshop Tennis. To “play” PT, usually some parameters are agreed on first, such as file format, time limits, or even artistic theme. One person creates a Photoshop file, then sends it to a second person. That player alters it—whether minimally by touch-up, or extensively, even perhaps throwing out the entire image and starting over—and returns the file. This back-and-forth can go on haphazadly or for a prearranged number of rounds; the end result is more than just a single image but an artistic sequence.
Just as no two artists are identical, no two art matches are the same either. The participants can range along the spectrum from collaboration—agreeing on a common theme, subject, motif, or purpose—to competition, with each trying to outdo the other in a demonstration of digital-art “chops.”
Although Photoshop Tennis developed and evolved spontaneously in several places, Coudal Partners, a Chicago design house, is where PT was finally formalized in a significant way. (Coudal also has one of the best freakin’ blogs on the planet, right on their home page, but nobody knows about them outside the graphic design community.)
Here are some sites where collaborative art is made, or where the gallery sections include extensive community comment and critique: