Customizing Bergen beamer theme

Question

Minimal (non-)Working Example:

\documentclass{beamer}
\usepackage{graphicx}
\usetheme{Bergen}
\usecolortheme[named=red]{structure}
\setbeamertemplate{footline}[text line]{%
  \parbox{\linewidth}{\vspace*{-8pt}\hfill \includegraphics[width=2cm]{Logo.jpg}}}
\setbeamertemplate{navigation symbols}{}
\begin{document}
\begin{frame}
\end{frame}
\end{document}

(Logo.jpg is my University's logo.) Result:

Aim:

For the title page, and:

For other pages. Questions:

1. How do I change the width of the vertical stripe?
2. How do I make said stripe extend into the footline?
3. How do I put the logo on the stripe?
4. How do I change the background?

(Note: Please disregard the size difference of the bottom-right logos, I just need to fix the width= in the \includegraphics command for that.)

Update

With @samcarter's comments, I was able to get the background in:

Code:

\documentclass{beamer}
\setbeamertemplate{background}
{\includegraphics[width=\paperwidth,height=\paperheight,keepaspectratio]{Background.png}}
\usetheme{Bergen}
\usecolortheme[named=red]{structure}
\setbeamertemplate{footline}[text line]{%
  \parbox{\linewidth}{\vspace*{-8pt}\hfill \includegraphics[width=1cm]{Logo.jpg}}}
\setbeamertemplate{navigation symbols}{}
\begin{document}
\begin{frame}
\end{frame}
\end{document}

So question 4 is solved. Her suggestions for 1-2 seem not to work for me. Question 3 is as of now unaddressed.

Answer 1

Creating a complete theme is exceeding the scope of this website, but here some quick hacks to create something similar:

\documentclass{beamer}

\usepackage{tikz}

\setbeamertemplate{background}
{\includegraphics[width=\paperwidth,height=\paperheight,keepaspectratio]{example-image}}

\setbeamercolor{sidebar}{bg=red!70!black}
\useoutertheme[height=0pt,width=1cm]{sidebar}

\setbeamertemplate{headline}{%
    \begin{tikzpicture}[remember picture, overlay]
        \node[xshift=-0.5cm,yshift=-0.5cm] at (current page.north east) {\tiny\insertframenumber};
    \end{tikzpicture}
}

\title[]{title}
\author[]{author names}

\setbeamertemplate{navigation symbols}{\raisebox{0.2cm}{\includegraphics[width=1cm]{example-image-duck}}\hspace*{0.2cm}}

\begin{document}

\begin{frame}[plain]
    \begin{tikzpicture}[remember picture, overlay]
        \fill[red!70!black] (current page.south west) rectangle ([xshift=2cm]current page.north west);
        \node at ([xshift=2cm,yshift=-1cm]current page.north west) {\includegraphics[width=2cm]{example-image-duck}};
    \end{tikzpicture}
  \titlepage
\end{frame}


\begin{frame}
  normal frame
\end{frame}
\end{document}

Answer 2

Here is the theme (file beamerthemebicocca.sty):

\NeedsTeXFormat{LaTeX2e}

\mode<presentation>

%--- Font theme (by default, Beamer loads \usefonttheme{default})

%--- Color theme
\usecolortheme[named=red]{structure}
\setbeamercolor{sidebar}{use=local structure,bg=local structure.fg}

%--- Inner theme (by default, Beamer loads \useinnertheme{default})
% Definition of the logo
\setbeamertemplate{logo}{\includegraphics[width=1cm]{example-image}}
% Title page
\addtobeamertemplate{title page}%
  {\thispagestyle{bicocca@navigation@titlepage}}{}
\def\ps@bicocca@navigation@titlepage{%
  \setbeamertemplate{sidebar canvas left}{%
    \usebeamercolor[bg]{local structure}%
    \vrule width .15\paperwidth height \paperheight}
  \setbeamertemplate{sidebar left}{\vskip 1cm%
    \hskip .1\paperwidth\includegraphics[width=2cm]{example-image}}
  \@nameuse{ps@navigation}}
% Background image
\setbeamertemplate{background}{%
  \pgfsetfillopacity{.05} % choose the opacity you wish here
  \includegraphics[height=\paperheight,width=\paperwidth]{example-image}
  \pgfsetfillopacity{1}}

%--- Outer theme (by default, Beamer loads \useoutertheme{default})
% No navigation bar
\beamertemplatenavigationsymbolsempty
% Default side bar (red stripe)
\setbeamersize{sidebar width left=1cm}


\mode<all>

and here is an example using the theme:

\documentclass{beamer}

\usetheme{bicocca}

\title{My Title}
\author{by Me}


\begin{document}

\maketitle

\begin{frame}
  A frame
\end{frame}

\end{document}

You should replace file example-image with your logo and adapt the different sizes.