My name is Eric van Poppel and my main contribution to wikipedia is images and sound files. Especially the latter is the big advantage of the Wikipedia Encyclopedia over a printed version.
Some samples:
File:2004327 Fighting Elephants.jpg
.jpg)
File:Saddlebilled Stork.jpg
File:2001588 Giant Petrel 2.jpg
.jpg)
More images and sounds can be found on my web site http://www.wildlifelands.com