Add dark background with image

The image is taken from

  http://commons.wikimedia.org/wiki/File:Blassenstein_Erlauftal_mit_Nebel_02_Panorama.JPG

By Uoaei1 (Own work) CC-BY-SA-3.0
(http://creativecommons.org/licenses/by-sa/3.0), via Wikimedia Commons.

beamerthemem.sty

@@ -165,12 +165,12 @@
 
 \newcommand{\rightTextArrow}{→}
 
-\newcommand{\statement}[1]{%
+\newcommand{\plain}[2]{%
   \begingroup
   \setbeamercolor{background canvas}{bg=mDarkTeal}
-  \begin{frame}[plain]
+  \begin{frame}{#1}
     \centering
-    \vfill\vspace{1em}\usebeamerfont{section title}\textcolor{white}{\scshape #1}\vfill
+    \vfill\vspace{1em}\usebeamerfont{section title}\textcolor{white}{\scshape #2}\vfill
   \end{frame}
   \endgroup
 }

demo.tex

@@ -148,6 +148,8 @@ text, \alert{accent} parts or show \textbf{bold} results.
   \end{quote}
 \end{frame}
 
+\plain{Dark background}{\vspace{-2em}\begin{center}\includegraphics[width=\textwidth]{images/valley.jpg}\end{center}}
+
 \section{Conclusion}
 
 \begin{frame}{Summary}
@@ -164,6 +166,6 @@ text, \alert{accent} parts or show \textbf{bold} results.
 
 \end{frame}
 
-\statement{Questions?}
+\plain{}{Questions?}
 
 \end{document}