Copied Green theme declaration from NixOS source here

svn path=/nixpkgs/trunk/; revision=13725

pkgs/data/misc/themes/green.nix

@@ -0,0 +1,5 @@
+{fetchurl, ...} : 
+fetchurl {
+  url = http://www.kde-look.org/CONTENT/content-files/58501-green.tar.gz;
+  sha256 = "0sdykpziij1f3w4braq8r8nqg4lnsd7i7gi1k5d7c31m2q3b9a7r";
+}

pkgs/top-level/all-packages.nix

@@ -6849,6 +6849,10 @@ let
     inherit fetchurl stdenv texinfo;
   };
 
+  themes = name: import (../data/misc/themes + ("/" + name + ".nix")) {
+    inherit fetchurl;
+  };
+
   ttf_bitstream_vera = import ../data/fonts/ttf-bitstream-vera {
     inherit fetchurl stdenv;
   };