I've added a few pictures and page edits here and there. Most of the things I have contributed to wikipedia are not discussed on this page, which is horribly out-of-date.
Misc
The page about the Munsell Color System has some decent diagrams, I think. Also, the page about HSL and HSV. More recently I'm pretty proud of the page about Lexell's theorem.
Photographs
I also have contributed a number of photographs to Wikipedia, most taken by myself, and others taken by friends and uploaded with permission. All my photographs (and those by friends that I've uploaded) are licensed under the Creative Commons Share-Alike 2.0 license (or some under a more recent version; note that the list below is probably quite incomplete):
