LBPlex is a theme that mimics Plex Media Server's website interface. Two versions are included in the package: LBPlex - which has the default item spacing on the sidebar and list view, and LBPlex Condensed - which has much tighter item spacing on the sidebar and list view. I have also replaced the volume "knob" with a regular slider.
All the colors in this theme are hard-coded with the exception of the Foreground (text) color in the LaunchBox Options\Legacy\Theme\Colors menu.
The Background Opacity slider in the LaunchBox Options\Visuals\Boxes menu has no effect right now. A fix is in-coming so this will work at a later date. Update: If you run the latest LaunchBox Beta (8.7-beta-1 or above) this is fixed.
The Fade Background slider in LaunchBox Options\Images\Default Background will adjust the brightness of the theme background image.