\documentclass{article}

\usepackage{graphicx,eso-pic,transparent}
\usepackage{lipsum}

\begin{document}

\AddToShipoutPictureBG*{%
  \AtPageUpperLeft{%
    \raisebox{-\height}{\includegraphics[width=\paperwidth]{k.png}}
  }
  \AtPageLowerLeft{%
    \makebox[\paperwidth]{\includegraphics[height=2.3cm]{g.png}}
  }%
}

\lipsum

\AddToShipoutPictureBG*{%
  \AtPageUpperLeft{%
    \transparent{0.5}\raisebox{-\height}{\includegraphics[width=\paperwidth]{k.png}}
  }
  \AtPageLowerLeft{%
    \transparent{0.5}\makebox[\paperwidth]{\includegraphics[height=2.3cm]{g.png}}
  }%
}

\end{document}