\ProvidesPackage{fixpauseincludegraphics}

\usepackage{graphicx}
\usepackage{tikz}

\setbeamercovered{transparent}

\let\oldincludegraphics\includegraphics
\renewcommand*{\includegraphics}[2][]{%
    \begin{tikzpicture}%
      {\node[opacity=\transparent@value/100] {\oldincludegraphics[#1]{#2}};}%
    \end{tikzpicture}%
}

% override of the original beamer@mixin transparent
\define@key{beamer@mixin}{transparent}[15]{%
    \def\beamer@uncoverbeforeactions{\ignorespaces\opaquenessCustom{#1}}%
    \def\beamer@uncoverafteractions{\ignorespaces\opaquenessCustom{#1}}%
}

% mostly a copy-and-paste of the original code from beamerbaseoverlay.sty
\def\opaquenessCustom#1{%
\only<1->{%
\beamer@actions{%
\gdef\transparent@value{#1}% here we change the custom transparency according to the pauses
\expandafter\xdef\csname beamer@oldcolorhook%
\the\beamer@coveringdepth\endcsname{\beamer@colorhook}%
\expandafter\xdef\csname beamer@oldpgfextension%
\the\beamer@coveringdepth\endcsname{\beamer@pgfextension}%
{\globalcolorstrue\colorlet{beamer@freeze\the\beamer@coveringdepth}{bg}}%
\xdef\beamer@colorhook{!#1!beamer@freeze%
\the\beamer@coveringdepth\beamer@colorhook}%
\gdef\beamer@pgfextension{!#1opaque}%
\color{.}%
}%
{%
\gdef\transparent@value{100}% here we initialize our custom transparency
\xdef\beamer@colorhook{\csname beamer@oldcolorhook%
\the\beamer@coveringdepth\endcsname}%
\xdef\beamer@pgfextension{\csname beamer@oldpgfextension%
\the\beamer@coveringdepth\endcsname}%
\color{.}%
}}%
}%

\setbeamercovered{transparent}