Since you like Zing! try searching the WindowBlinds Gallery for other JJ Ying themes. Just type the name of the author in the search box. Some other top notch authors Mike Bryant, danilloOc(has some very nice subtle designs) and essorant. You can also use WindowBlinds to adjust coloration, saturation and gamma settings to possibly find that ideal that is just right for your tastes.
There are other numerous authors whom I like very much but, I thought you should start here.
IFlex by danilloOc is very easy on the eyes. He has some other great themes as well. aerial also comes to mind. WindowBlinds can be set to remove all color and turn these themes into all black and white if you don't like the high color buttons in aerial for example.
nuage by essorant also comes to mind, it also comes in a gray version and you can experiment with WindowBlinds adjustments with these as well.
My advice is find the theme that has the right style for you and then try tweaking that little bit of extra you're looking for with WindowBlinds settings. And, don't forget a theme can look very different and much more subtle simply by reducing saturation and adjusting the gamma settings.