Avec `tikz` on peut faire quelque chose comme ça :
\documentclass{beamer}
\usepackage{tikz}
\begin{document}
\begin{frame}
\begin{figure}
\begin{tikzpicture}
\node at (0,0) {\includegraphics[width=.6\textwidth]{example-image-a}};
{\includegraphics[width=.6\textwidth]{example-image-duck}};
\node at (-1,-0.5) {\includegraphics[scale=0.25]{example-image-b}};
{\includegraphics[scale=0.25,page=2]{example-image-duck}};
\end{tikzpicture}
\caption{blabla}
\end{figure}
\end{frame}
\end{document}
Une autre possibilité sauf des extensions :
\documentclass{beamer}
\begin{document}
\begin{frame}
\begin{figure}
\begin{picture}(200,150)
\put(0,0){\includegraphics[width=.6\textwidth]{example-image-a}}
\put(40,30){\includegraphics[scale=0.25]{example-image-b}} \put(0,0){\includegraphics[width=.6\textwidth]{example-image-duck}}
\put(40,30){\includegraphics[scale=0.25,page=2]{example-image-duck}}
\end{picture}
\caption{blabla}
\end{figure}
\end{frame}
\end{document}
![alt text][1]
[1]: https://texnique.fr/osqa/upfiles/Screen_Shot_2019-05-11_at_16.01.53.pnghttps://texnique.fr/osqa/upfiles/Screen_Shot_2019-07-05_at_14.03.11.png
