One of the most often mentioned concerns at the KDE booth at LinuxTag was the question if Plasma would force the user to have a black panel. While we did have a second machine showing another theme to resolve all doubts it showed that not all users now yet the power of Plasma theming.
KDE is well known for the possibilities to configure it just like you want. And Plasma is no exclusion of this rule. Instead, the theming is well documented and there are already many user themes available at kde-look.org.
However, the shots shown below were made with the KDE 4.1 development version, and not all Plasma themes were created or tested for that version. Please keep this in mind and be tolerant regarding smaller issues. Additionally, I picked almost all themes which were offered via the GetHotNewStuff dialog, so there are themes of all types of quality.