I created another openbox theme, a slim, minimalistic one this time. There are two different sets of buttons included. Additionally i did a similar rezlooks gtk theme, which is also included in the tarball.
Openbox is a free, stacking window manager for the X Window System, licensed under the GNU General Public License. Originally derived from Blackbox 0.65.0, Openbox has now been totally re-written in the C programming language and since version 3.0 is no longer based upon any code from Blackbox. Wikipedia