\DocumentMetadata{tagging = on, pdfstandard = ua-2}

\documentclass{ltx-talk}

\title{Background images for single frames}

\begin{document}

\begin{frame}
  Some text

  \AddToHookNext{shipout/background}
    {\put(0cm, -\paperheight)
        {\includegraphics[artifact, width = \paperwidth, height = \paperheight]
            {example-image-a}}}
\end{frame}

\begin{frame}
  Some text on a plain background
\end{frame}

\begin{frame}
  Some text with a centred background image
  \AddToHookNext{shipout/background}{\put (0.5\paperwidth,-0.95\paperheight) {\clap{\includegraphics{example-image}}}}
\end{frame}

\begin{frame}
  Some text on a plain background
\end{frame}

\end{document}