Packages with the thumbnail use flag

kde-apps / kdecore-meta : kdecore - merge this to pull in the most basic applications

  • Install kde-apps/ffmpegthumbs and kde-apps/thumbnailers for thumbnail generation in kde-apps/dolphin

kde-apps / kdegraphics-mobipocket : Library to support mobipocket ebooks

  • Enables thumbnail generation

media-sound / beets : Media library management system for obsessive-compulsive music geeks

  • Enable album thumbnails generation