MPlayerThumbs is a thumbnail generator for all KDE file managers (konqueror, dolphin, ...)
It needs mplayer (of course) to generate thumbnails, and it contains no linking to any library, so in a x86_64 system you can freely use the 32bit mplayer binary with win32codecs by configuring the application launching the mplayerthumbsconfig helper application.

Quickly installing mplayerthumbs (install instruction adapted from the kmplayer package, thanks folks!)
Untar the source package
  tar xfj mplayerthumbs-<version>.tar.bz2
Create a build directory, eg /tmp/mplayerthumbs-build and enter this directory
Set your environment for building KDE4 apps
  export QTDIR=path-to-qt4
  export KDEDIR=path-to-kde4
  export KDEDIRS=$KDEDIR
  export KDE_BUILD=$KDEDIR
  export DBUSDIR=$KDEDIR
  export LD_LIBRARY_PATH=$QTDIR/lib:$KDEDIR/lib:$LD_LIBRARY_PATH
  export PKG_CONFIG_PATH=$DBUSDIR/lib/pkgconfig:/usr/lib/pkgconfig
  export PATH=$QTDIR/bin:$KDEDIR/bin:$PATH
Run cmake
  cmake -DCMAKE_INSTALL_PREFIX=$KDEDIR -DCMAKE_BUILD_TYPE=release path-to-mplayerthumbs-source
Run make
  make
Install as root
  make install

Enjoy!


