I discovered a link to an open source project that Cell Shades Quake 3 Arena. It's hosted on SourceFORGE under the "GNU General Public License (GPL)"
http://q3cellshading.sourceforge.net/So I checked it out myself and see if it was really worth it. The bad part of this is that it only works, well the binaries anyway, with the retail version of Quake 3 Arena. The good news that I discovered, while going through some of their sourceforge pages, is someone managed to get it to work with the IOQuake3 exe. (
Short link to Tracker topic)
Now I know nothing of programming and of the sort, so I wouldn't know how difficult to port it. This would be one of those fun things that people could use when they get tired of how OpenArena currently looks and needs a change for a while. Hell, I wouldn't mind playing in this kind of setting with OpenArena.