Hello May,
There is the best wikipedia graphist I know of: User:LadyofHats, a lady from Mexico. She stands out above others, for both technic and artistic skills.
Cartographers are by definition more technical, which get incremented by elegant stylesheets and icons. By chronological order, best cartographers are Planemand (in), STyx (fr), Sting (fr), Séhmur (fr), myself/Yug (fr), NordNordWest (aka NNW, de), TUBS (de), Thoroe, Bourrichon (fr), Flappiefh (fr), MapMaster (en), Ikonact (fr). Each of us is also a graphist, while our artistic side are very variable.
These wikigraphists collectively made thousands graphic improvements on various Graphic Labs (en:Graphic Lab, fr, de, es, ...). The Graphic labs all together made about 8.000 images and 6.000 maps for the German and French. We got years of cross teaching and brain storming on shapes, styles, color, techniques in this amateur context as well as interaction with the Wikipedia community to help define its graphic needs and associated response.
I don't think any of us, as volunteers, have your firepower : the ability to spend 1 week, one month on an heavy project to make it *happen*. But wikigraphists have an extensive experience which make them a great pool of beta testers, feedbacks, and lead users on graphic issues. These guys are visual, smart and curious, and may be interested to learn design skills & tools from you guys. Poke us anytime you wish, be proud to show us your beta. The French, German community are the most powerful and understand English smoothly. The English community then follow. We will be happy see how pro works & learn from you !