Like this?

As Torbjørn T. mentioned, your question is very related (i.e. a duplicate) to
this question and/or this question, so I adapted their provided solutions, while adding row colors and removing the unnecessary label:
\documentclass{article}
\usepackage{graphicx}
\usepackage[export]{adjustbox}
\usepackage[table]{xcolor}
\usepackage{array}
\begin{document}
\begin{table}[htbp]
\caption{My composed image}
\label{table-1}
\centering
\arrayrulecolor{white}
\setlength\arrayrulewidth{2pt}
\begin{tabular}{|>{$}c<{$} |c|c|c|c|}
\rowcolor{blue}
\hline
& \textcolor{white}{condition A}
& \textcolor{white}{condition B}
& \textcolor{white}{condition C}
& \textcolor{white}{condition D} \\ \hline
\rowcolor{blue!50}
N=1 & \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image} \\ \hline
\rowcolor{blue!25}
N=2 & \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image} \\ \hline
\rowcolor{blue!50}
N=3 & \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image}
& \includegraphics[width=2cm,margin=0pt 3pt,valign=c]{example-image} \\
\end{tabular}
\end{table}
\end{document}
\includegraphicsof packagegraphicxfor image inclusion and packagexcolorwith optiontablefor color stuff and alternating row colors. – Heiko Oberdiek Oct 21 '16 at 17:26labelwithout acaptionis not useful intableenvironments because without a caption handle there is nothing to refer to. Should also give you a log message. Here you are even overwriting the firstlabel{table-1}by the second\label{table-3}. – Matthias Arras Oct 22 '16 at 07:02