Modification of text height in a beamer slide

Question

I'm using Beamer to do some slides and figured out how I could put some pictures where I wanted at the top of the slide using the textpos package. However, I would like to redefine the \textheight of the slide to be able to adjust pictures to the remaining height of the slide. The idea of such a slide is to replace the usual title by the association of the journal's cover and the title of the published article. Then, I'd use the slide to show the results.

Here is a mwe:

    \documentclass{beamer}
    \usepackage{graphicx}
    \usepackage[absolute,showboxes,overlay]{textpos}
    \textblockorigin{10mm}{10mm} 
    \begin{document}

    % cover of the journal
    \begin{textblock*}{15mm}[0.5,.5](0cm,0.5cm) 
    \includegraphics[height=20mm, keepaspectratio]{path-to-pictureA-file}
    \end{textblock*}

    % title of the journal
    \begin{textblock*}{100mm}[.5,.5](60mm,0.5cm)
    \includegraphics[height=20m]{path-to-pictureB-file}
    \end{textblock*}

    % main result
    \includegraphics[height=\textheight, width=\textwidth, keepaspectratio]{image.eps}

Thanks a lot for your help

PS: I would like to use this modification only in the slides I want to show as explained above. The other slides will be shown as usual. My goal is to figure out then how to define a new environment to get a more efficient code.

Answer 1

Why not something simpler?

\documentclass{beamer}
\usepackage{calc}
\begin{document}
\begin{frame}
  \centering
  \includegraphics[height=20mm]{example-image-16x9}
  \includegraphics[height=20mm]{example-image-16x9}
  \includegraphics[height=20mm]{example-image-16x9}

  \includegraphics[height=\textheight-20mm, width=\textwidth, keepaspectratio]{tiger}
\end{frame}
\end{document}