\documentclass[%
%,sanserif
%,a4paper
]{ptbposter}
\usepackage{ptbposter-tcb}

\phone{+49-30-3481-7316}
\fax{+49-30-3481-7503}
\email{Rolf.Niepraschk@ptb.de}
\workingGroup{7.54 Vakuummetrologie}
\department{7.5 Wärme und Vakuum}
\location{10587 Berlin}
\street{Abbestraße 2--12}
\QRcode{http://www.ptb.de/cms/fachabteilungen/abt7/fb-75/ag-754.html}

\Author{Rolf}{Niepraschk}

%\logo{Logo754.pdf}

\colorlet{backgroundTop}{IndianRed3!10}
\colorlet{backgroundBottom}{IndianRed3!90}
\posterSet{showframe=false,columns=3,rows=3}

\title{Poster-Test (\texttt{tcolorbox}, \textup{Ti\textit{k}Z}) -- Nr.~2}

\begin{document}
  \begin{posterboxenv}[title=John Lennon]{name=John,column=1}
    \includegraphics[width=\linewidth]{John.png}
  \end{posterboxenv}
  \begin{posterboxenv}[title=Paul McCartney]{name=Paul,column=3}
    \includegraphics[width=\linewidth]{Paul.png}
  \end{posterboxenv}
  \begin{posterboxenv}{name=Beatles,column=2,at=middle}
    \includegraphics[width=\linewidth]{The_Beatles_official_logo.pdf}
  \end{posterboxenv}
  \begin{posterboxenv}[title=George Harrison]{name=George,column=1,above=bottom}
    \includegraphics[width=\linewidth]{George.png}
  \end{posterboxenv}
  \begin{posterboxenv}[title=Ringo Starr]{name=Ringo,column=3,above=bottom}
    \includegraphics[width=\linewidth]{Ringo.png}
  \end{posterboxenv}

  \tikzset{arrow/.style={draw=PTBcolor,line width=1ex,->,-{Latex[length=4ex]}}}

  \draw[arrow] (TCBPOSTER@John.south) to 
    [out=-90,in=150] ([yshift=1.5em]TCBPOSTER@Beatles.west);
  \draw[arrow] (TCBPOSTER@Paul.south) to
    [out=-90,in=30] ([yshift=1.5em]TCBPOSTER@Beatles.east);  
  \draw[arrow] (TCBPOSTER@George.north) to
    [out=90,in=210] ([yshift=-1.5em]TCBPOSTER@Beatles.west);  
  \draw[arrow] (TCBPOSTER@Ringo.north) to
    [out=90,in=-30] ([yshift=-1.5em]TCBPOSTER@Beatles.east);  
\end{document}