I completed the new theme today and named it Kohlenstoff (german word for carbon).
The theme has still some problems I can't fix because they are caused by the applications.
-Firefox menubar-text is black (there is a userchrome.css in the theme included which fixes this problem)
-OpenOffice menubar text is black
-Rhythmbox sidebar listexpanders are light grey (why???)
-Unreadable colors in non-native gtk apps (O.Office, Firefox etc.)
If somebody has a solution for these problems, please share it.
You can see bigger screenshots on my blog (follow the download link).