beamer: Scaling document icons in the bibliography

Question

Bibliographies can be typeset in a smaller font size by redefining the \bibfont macro (if one uses natbib or biblatex) or by simply appending the definition of \thebibliography. This also works with the beamer class; however, switching to a smaller font size leaves beamer's document icons at the start of each bibitem unchanged. How can I scale those icons down to, say, 75% of their original size?

(From Removing document icons from a Bibtex bibliography in Beamer, I gather that an answer is likely to involve some clever use of \setbeamertemplate{bibliography item}.)

\documentclass{beamer}

\usepackage{etoolbox}
\apptocmd{\thebibliography}{\scriptsize}{}{}

\usepackage{filecontents}

\begin{filecontents}{\jobname.bib}
@article{Bli74,
  author = {Blinder, Alan S.},
  year = {1974},
  title = {The economics of brushing teeth},
  journal = {Journal of Political Economy},
  volume = {82},
  number = {4},
  pages = {887--891},
}
\end{filecontents}

\begin{document}

\nocite{*}

\bibliographystyle{plain}

\begin{frame}
\bibliography{\jobname}
\end{frame}

\end{document}

Answer 1

Bibliography items are inserted using \pgfuseimage. You could redefine this before the bibliography and scale it the way you want to using commands from graphicx (included by beamer by default:

\renewcommand{\pgfuseimage}[1]{\includegraphics[scale=.75]{#1}}

The above scales the image to 75% of its original size.

This should be issued outside the frame environment, before calling \bibliography. Here's your complete minimal example:

\documentclass{beamer}% http://ctan.org/pkg/beamer

\usepackage{etoolbox}% http://ctan.org/pkg/etoolbox
\apptocmd{\thebibliography}{\scriptsize}{}{}

\usepackage{filecontents}

\begin{filecontents}{\jobname.bib}
@article{Bli74,
  author = {Blinder, Alan S.},
  year = {1974},
  title = {The economics of brushing teeth},
  journal = {Journal of Political Economy},
  volume = {82},
  number = {4},
  pages = {887--891},
}
\end{filecontents}

\begin{document}

\nocite{*}

\bibliographystyle{plain}

\renewcommand{\pgfuseimage}[1]{\scalebox{.75}{\includegraphics{#1}}}

\begin{frame}
\bibliography{\jobname}
\end{frame}

\end{document}