Two figure side-by-side in a single column of tikzposter?

This works:

\documentclass{tikzposter}

\title{The Title}
\author{The Author}

\begin{document}

\maketitle

\block{A Title}{%
\begin{center}
\begin{minipage}{0.45\linewidth}
  \centering
  \begin{tikzfigure}[Caption of figure1]
  \includegraphics[height = 10cm]{example-image-a}
  \end{tikzfigure}%
\end{minipage}\hfill
\begin{minipage}{0.45\linewidth}
  \centering
  \begin{tikzfigure}[Caption of figure2]
  \includegraphics[height = 10cm]{example-image-b}
  \end{tikzfigure}%
\end{minipage}
\end{center}
}

\end{document}

You probably might want to control the figures' width instead of their height, as in

\includegraphics[width=.75\linewidth]{image}

and using the optional argument for minipage, you can adjust vertical alignment; for example, using b (bottom alignment):

\documentclass{tikzposter}

\title{The Title}
\author{The Author}

\begin{document}

\maketitle

\block{A Title}{%
\centering
\begin{minipage}[b]{0.45\linewidth}
  \centering
  \begin{tikzfigure}[Caption of figure1]
  \includegraphics[width=.7\linewidth,height=5cm]{example-image-a}
  \end{tikzfigure}%
\end{minipage}\hfill
\begin{minipage}[b]{0.45\linewidth}
  \centering
  \begin{tikzfigure}[Caption of figure2]
  \includegraphics[width=.7\linewidth,height=10cm]{example-image-b}
  \end{tikzfigure}%
\end{minipage}%
}

\end{document}

\column{0.5}
\block{A figure}
 {
        \begin{tikzfigure}
            \includegraphics[width=0.2\textwidth]{thankyoupostit.png}
            \includegraphics[width=0.2\textwidth]{thankyoupostit.png}
            \includegraphics[width=0.2\textwidth]{thankyoupostit.png}
        \end{tikzfigure}
  }

We can put as many as figures very simply as done in above code snippet. But for this the total width requirement for images should be less than or equal to the size of column.