This is my first Openbox theme. :)
I made it specifically to go with the Aurora-looks GTK theme, but it will probably look good with others as well.
Here is a link to the Aurora GTK Engine (includes the Aurora-looks theme):
To install this, just extract the .tar.gz and place the folder in your ~/.themes directory. Alternatively, you can turn the extracted folder into a .obt file with obconf and then install that from within obconf.