# How to create Placeholder for missing figure?

I'm writing my paper using texlive2013.As for me,it is rather annoying to swich between writing and plotting figures.So I'd like to create a dummy figure when I was writing to avoid disturbance and add figures back later.I found a nice solution here:

However,not only were the missing figures,other normal figures were replaced as well.Is there a way to get it around?

A small workaround, but not perfect for sure (depending on the graphics extension, it might fail) -- I use the \IfFileExists in a slightly redefined \includegraphics command. It test for four extensions (all in lower case) (.eps,.pdf, .jpg and .png)

\documentclass{scrbook}

\usepackage{blindtext}
\usepackage{graphicx}
\usepackage{tcolorbox}

\let\StandardIncludeGraphics\includegraphics%
\renewcommand{\includegraphics}[2][]{%
\IfFileExists{#2.eps}{%
\StandardIncludeGraphics[#1]{#2}%
}{%
\IfFileExists{#2.pdf}{%
\StandardIncludeGraphics[#1]{#2}%
}{ % No, no .pdf, try *.jpg
\IfFileExists{#2.jpg}{%
\StandardIncludeGraphics[#1]{#2}%
}{
\IfFileExists{#2.png}{%
\StandardIncludeGraphics[#1]{#2}%
}{%
\begin{tcolorbox}[width=6cm,height=4cm,arc=0mm,auto outer arc]
\end{tcolorbox}
}
}
}
}%
%
}% End of command

\begin{document}

\chapter{First one}
\blindtext

\begin{figure}
\begin{center}

\includegraphics[width=10cm,height=8cm]{some_file}
\caption{My demo figure}
\end{center}
\end{figure}
\blindtext[2]

\end{document}


The mentioned file some_file does not exist at all in my paths.