\documentclass[demo]{book}
\usepackage{graphicx}
\usepackage{kpfonts}
\usepackage[explicit]{titlesec}
\usepackage{xcolor}
\usepackage{tikz}
\usepackage{eso-pic}
\usepackage{eso-pic}

\colorlet{WLEBlue1}{blue}

\newcommand*\headerbg{
  {\begin{tikzpicture}[remember picture,overlay]
    \node[yshift=-3cm] at (current page.north west)
      {\begin{tikzpicture}[remember picture, overlay]
        \draw[fill=WLEBlue1] (0,0) rectangle
          (\paperwidth,3cm);
          \node (label) at (10,1.5){
            \includegraphics[width=660pt]{graphics/pagestyle/header_bg.png}
          };
          \node (label) at (1.4,1.5){
            \includegraphics[width=60pt]{graphics/pagestyle/WLE_Logo.png}
          };
       \end{tikzpicture}
      };
   \end{tikzpicture}
  }
  }

\newcommand\BackgroundPic{
\headerbg
\put(0,0){
\parbox[b][\paperheight]{\paperwidth}{%
\vfill
\centering
\begin{tikzpicture}[remember picture,overlay]
    \node at (-10,12.5)
      {\begin{tikzpicture}[remember picture, overlay]
            \draw [WLEBlue1, fill=WLEBlue1] (0,0) -- (0.05,0) -- (0.05,-22.2) -- (0.25,-22.2) -- (0.25, -23) -- (0, -23);
       \end{tikzpicture}
      };
\end{tikzpicture}
\begin{tikzpicture}[remember picture,overlay]
\node at (8.5,12.5)
      {\begin{tikzpicture}[remember picture, overlay]
            \draw [WLEBlue1, fill=WLEBlue1] (-1, -23) -- (0, -23) -- (0, -22) -- (-0.08, -22) -- (-0.08, -22.92) -- (-1, -22.92);
       \end{tikzpicture}
      };
\end{tikzpicture}
\vfill
}}}

\usepackage{lipsum}

\begin{document}

\AddToShipoutPicture{\BackgroundPic}

\tableofcontents
\chapter{Test}
\section{Test}
\section{Test}
\section{Test}
\section{Test}
\section{Test}
\section{Test}
\section{Test}
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\chapter{Test}
\section{Test}
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\chapter{Test}
\section{Test}
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\chapter{Test}
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\chapter{Test}
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\chapter{Test}
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\chapter{Test}
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\chapter{Test}
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\chapter{Test}
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\chapter{Test}
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\end{document}