There is qtcurve style, with Metalized texture for backgrounds:
Unfortunally, when texture is used for window background, default background color is not drawed for kwin decoration in all cases, and you have either use opaque texture or don't use qtcurve with kwin. In this theme transparent texture is used only for menu.
Original theme is Studio Plastic with some changes:
For screenshot above KXStudio color scheme is used: