This is what I use, I have a custom user template for company colors for the titles blocks...
in preamble
\defbeamertemplate*{title page}{customized}[1][]
{
\begin{flushright}
\usebeamercolor{structure}
\usebeamerfont{title}\inserttitle\par
\usebeamerfont{subtitle}\usebeamercolor{subtitle}\insertsubtitle\par
\bigskip
\usebeamerfont{author}\insertauthor\par
\usebeamerfont{institute}\insertinstitute\par
\usebeamerfont{date}\insertdate\par
\end{flushright}
}
\title[]{yourtitle}
\subtitle[]{Subtitle}
\author[] {you}
\institute[] {company}
\date[] {tody is \today}
\subject{Subject of presentation}
Here you define the backgroud of the slides, I use only a custom footer of page width
\usebackgroundtemplate%
{%
\vbox to \paperheight{
\vfill
\includegraphics[width=\paperwidth]{slide} %your picture
}%
}
And first slide
%--- the titlepage frame -------------------------%
{\usebackgroundtemplate%
{%
\includegraphics[width=\paperwidth,height=\paperheight]
{yourpicture}
\begin{frame}[plain]
\titlepage
\end{frame}
}