Dear Maintainer,

The thumbnails are hard-coded to be stored in
$HOME/.cache/thumbnails/.  It's a good place, but eog should support
some environment variables to conform to this standard:

http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

Since thumbnails are shared by many apps, having different apps choose
different directories breaks the benefit of that sharing.  Gimp, for
example, stores thumbnails in $XDG_CACHE_HOME/thumbnails/.  ATM, users
who want to exploit the thumbnail are forced to set $XDG_CACHE_HOME to
$HOME/.cache/ to cater for eog.

There should also be an "Environment" section added to the manpage,
which should document any of these variables that eog ends up using:

    $XDG_DATA_HOME
    $XDG_CONFIG_HOME
    $XDG_DATA_DIRS
    $XDG_CONFIG_DIRS
    $XDG_CACHE_HOME
    $XDG_RUNTIME_DIR