I want to have a following layout of pictures:

I'm using subfigures:
\documentclass[12pt, a4paper]{report}
\usepackage{caption}
\usepackage{floatrow}
\usepackage{subcaption}
\usepackage{graphicx,xcolor}
\usepackage[framemethod=tikz]{mdframed}
\newcommand{\fakeimage}{{\fboxsep=-\fboxrule\fbox{\rule{0pt}{3cm}\hspace{4cm}}}}
\begin{document}
\begin{figure}
\centering
\begin{subfigure}{.3\linewidth}
\centering
\fakeimage
\caption{Image}\label{fig:image1}
\end{subfigure} %
\hfill
\begin{subfigure}{.3\linewidth}
%\centering
\fakeimage
\caption{Image}\label{fig:image12}
\end{subfigure}
\hfill
\begin{subfigure}{.3\linewidth}
\centering
\fakeimage
\caption{Image}\label{fig:image12}
\end{subfigure}
\hfill
\begin{subfigure}{\linewidth}
\centering
\fakeimage
\caption{Image}\label{fig:image3}
\end{subfigure}
\RawCaption{\caption{General caption}
\label{fig:images}}
\end{figure}
\end{document}
I'm getting:

