The KDE Plasma team is inviting everyone to participate in a contest to create Plasma themes from which a select few will be chosen to be included as a part of the upcoming KDE 4.1 release. This is a great opportunity to contribute to a very visible component of the KDE project, the Plasma desktop.
A great feature of Plasma is the ability to theme components of the desktop using Scalable Vector Graphics (SVGs). This means there is no need for you to know C++ or any other programming language to create a great looking theme.
You only need to know how to use one of many graphics tools (e.g. Krita, Inkscape, The GIMP, Karbon, etc.) and that is all. Depending on your prowess with such tools, you can create great looking plasma themes in as little as an hour.
You can find a quick guide to creating Plasma themes in the Creating a Plasma Theme in 7 Easy Steps Techbase article.
Have fun! The Plasma Team.