I have a problem with themes in Openbox, I checked every theme and none of them changed the background or the style of the windows! Openbox only changes the titlebars and the right-click menus. What happen?
Leiaz is right. Openbox is is just a window manager and can't change the theme of GTK+, Qt or any other kind of GUI framework or the background.
This is the difference between a desktop environment (DE) like KDE or Gnome and just a window manager like Openbox.
A DE is designs as a whole desktop with a window manager, a desktop manager, a panel, and many more. Thanks to this fact a DE can provide a complete and matching theme for all these sub parts.
Openbox on the other hand can only manage its own theme, since it does not know what else is install. It is only a window manager.
LXDE is a DE that uses Openbox as a window manager and they have build LXAppearance, a tool to manage the look and feel of LXDE.
You can build your own DE, but you have to do some steps by hand to get a consistent theme.
For one you will need to find a tool to set your background image. For this I use the image viewer feh it has packages for Arch Linux, Debian, FreeBSD, Gentoo, OpenBSD and Ubuntu.
Then you will need to set your GUI for GTK+, Qt and everything else your use.
For my setup I use "Clearlooks Compact" which is a GTK+ theme that supports GTK+2 and GTK+3 and I use the GTK compatible mode of Qt in
Then there are other tools like panels and such which all might need there own configuration to match with the theme. But this is material for a whole new question.
So if you want a nice theme you ether switch to a full DE or stay whit Openbox and build your own DE. If you choose the second one, you will need to do a lot of work, but you will also learn a lot about desktop environments.
Openbox is a window manager, it only manages windows' positions and their title bars, and the Openbox menu. Openbox themes aren't supposed to change anything else. For inside the windows, you want to set the Gtk theme or Qt style (or it can be application specific).
The terminal on top in the second screenshot is listing all themes and font used.