Since you want to suppress the coloured box for the title, you'll need a redefinition of the title page
template defined by the default
inner theme used by Madrid
.
To suppress the footline from the titlepage, you can use the plain
option for the frame.
To include the image, you can set the background canvas
template, using a standard \includegraphics
(of course, instead of papiro
, use one of your own images) command.
To keep all these changes local, you can use the grouping mechanism.
A little example:
\documentclass{beamer}
\usetheme{Madrid}
\makeatletter
\defbeamertemplate*{title page}{mytitlepage}[1][]
{
\vbox{}
\vfill
\begin{centering}
\begin{beamercolorbox}[sep=8pt,center,#1]{}
\usebeamerfont{title}\inserttitle\par%
\ifx\insertsubtitle\@empty%
\else%
\vskip0.25em%
{\usebeamerfont{subtitle}\usebeamercolor[fg]{subtitle}\insertsubtitle\par}%
\fi%
\end{beamercolorbox}%
\vskip1em\par
\begin{beamercolorbox}[sep=8pt,center,#1]{author}
\usebeamerfont{author}\insertauthor
\end{beamercolorbox}
\begin{beamercolorbox}[sep=8pt,center,#1]{institute}
\usebeamerfont{institute}\insertinstitute
\end{beamercolorbox}
\begin{beamercolorbox}[sep=8pt,center,#1]{date}
\usebeamerfont{date}\insertdate
\end{beamercolorbox}\vskip0.5em
{\usebeamercolor[fg]{titlegraphic}\inserttitlegraphic\par}
\end{centering}
\vfill
}
\makeatother
\title{A Modified Beamer Theme}
\subtitle{Background image and no special decorations}
\author{The Author}
\institute{The Institute}
\begin{document}
\begingroup
\setbeamertemplate{background canvas}{\includegraphics[width=\paperwidth,height=\paperheight]{papiro}}
\setbeamertemplate{navigation symbols}{}
\begin{frame}[plain]
\maketitle
\end{frame}
\endgroup
\begin{frame}
\frametitle{A regular frame}
test
\end{frame}
\end{document}