TempuraFlat GTK2, GTK3, Openbox and Tint2 Themes
This is based on a really old GTK2 theme, Tempura. I applied the colors and flat shapes to one of the excellent Bunsen themes. This was a manageable task for GTK2, but GTK3... that took me a while. The amount of config text must be about ten times of the GTK2 config text. Upside: It's all CSS.
I created different variations for the Openbox themes, mostly because I need to be able to recognize if a window has focus, even if it's undecorated. So, slightly thicker borders and contrasting colors.
The GTK Murrine engine, and the Mist engine for nice looking checkboxes.
I'm not sure about GTK3, I don't think it requires any particular engine.
If you're using the Tint2 panel, you can try the media-player-info plugin.
Just clone it to wherever you like, then run
If you omit "directory", it will default to
If you are using e.g. lxpanel, you can try the included 30px panel background.