Collecting and making your own mixture of parts from official LEGO minifigs is great. Some people also make their own custom minifigs, by painting and modifying standard LEGO parts.
This collection is by Julian Fong (click on the name for a link to his bio). He has done Computer Science, and works at Pixar. Have a look at a more detailed version of the photo above, and some of his other great stuff at http://www.flickr.com/photos/levork/
A story about his creations at Comics Alliance: link- Lego Comic Book Covers By Pixar's Julian Fong