\documentclass{article}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{spy}
\def\imgfile{../graphics/none.png}

\begin{document}

% \includegraphics as a node in tikz, see ar5iv#215
\begin{figure*}
  \begin{tikzpicture}
    \begin{scope}[spy using outlines={rectangle,blue,magnification=2.5,size=3cm}]
    \node {	\includegraphics[height=3cm]{\imgfile}};
    \end{scope}
  \end{tikzpicture}

  \begin{tikzpicture}
    \begin{scope}[spy using outlines={rectangle,blue,magnification=2.5,size=3cm}]
    \node {	\includegraphics[height=3cm]{\imgfile}};
    \end{scope}
  \end{tikzpicture}
  \caption{tikz nodes with includegraphics}
\end{figure*}

\end{document}