Thanks to KDS Sahambi, the first extra theme, Smoke 1.5b for Nvu, is now available:

  1. Right-click on the following link and save the jar on your hard-disk
  2. Launch Nvu
  3. Open Tools > Themes
  4. Click on Install button, select the file you just saved, click OK
  5. In the Themes manager, select the theme that was just installed, and click the "Use that theme" button
  6. Quit Nvu, relaunch and enjoy!

Known problems: a few icons are not visible, e.g. fixed and flexible space in Customize Toolbar.