Location for user installed plugin libraries and icons

[Jon Gough <jonsgough@gmail.com>]

    Hi List,
         I am working on a user driven plugin management process for an
      application which is installed via a 'deb' file. The application
      is installed using 'root' privileges, but the plugins need to be
      installable by the user without root privileges. The plugins will
      consist of libs, icons, etc. that are used to 'run' the plugin and
      user updateable config files used to 'control' the plugin. 
      
         If the plugin was installed by a 'deb' file it would put libs
      and supplied icons in a system area, i.e. /usr or /usr/local, and
      the updateable config files in a user writeable area, i.e.
      $HOME/.<application>/. What would be a suitable location for
      the libs, icons, etc. for the user installed plugin? 
      
      Many thanks
      Jon