Laying out multiple images in a figure

Organizing image in table with measurement of smaller image height:

\documentclass{article}
\usepackage[export]{adjustbox}
\usepackage[skip=1ex]{caption}
\usepackage{booktabs, multirow}
\newsavebox\image

\begin{document}
    \begin{figure}[tb]
    \centering
\caption{asd}
\label{fig:myimportantfigure}
    \setlength\tabcolsep{1pt}
    \setkeys{Gin}{keepaspectratio}
    \sbox\image{\includegraphics[width=0.225\linewidth,valign=t]{example-image-a}}
\begin{tabular}{c p{0.225\linewidth}p{0.225\linewidth}}
\multirow{2}{*}{\includegraphics[height=\dimexpr2\ht\image+2\dp\image+2pt,valign=t]{example-image-duck}}
    & \usebox\image & \includegraphics[width=\linewidth,valign=t]{example-image-b} \\
    \addlinespace[2pt]
    & \includegraphics[width=\linewidth,valign=t]{example-image-a} & \includegraphics[width=\linewidth,valign=t]{example-image-b} 
\end{tabular}
    \end{figure}
\end{document}

With minipages and valign=t from the adjustbox package:

\documentclass{article}

\usepackage{graphicx}

\usepackage[export]{adjustbox}

\begin{document}    
\begin{figure}
\caption{asd}
\label{label}
    \begin{minipage}[t]{0.5\textwidth}
         \includegraphics[width=.9\linewidth,valign=t]{example-image-a}
     \end{minipage}%
     \begin{minipage}[t]{0.5\textwidth}
         \includegraphics[width=.45\linewidth,valign=t]{example-image-b}\hfill
         \includegraphics[width=.45\linewidth,valign=t]{example-image-c}
         \includegraphics[width=.45\linewidth,valign=t]{example-image-b}\hfill
         \includegraphics[width=.45\linewidth,valign=t]{example-image-c}
     \end{minipage}
\end{figure}

\end{document}