How to insert a background image in a beamer frame?

Apologies in advance if my question is very basic. I am still learning my beamer skills, so please bear with me.

I want to insert a background image in a beamer frame and use this "frame" as a beamer frame. I want to insert different background images on different frames. Towards this end, I tried

\usebackgroundtemplate{\includegraphics[width=\paperwidth]{../images/crayons.png}}


on a specific frame to insert a background image, but I was unsuccessful. Am I missing any package? Or is there a different way of doing this?

I found this question here about inserting image but not as a background. In addition to inserting a background image, I also want to add text to the frame. (It is highly likely that I could not understand the questions correctly)

As a side note, if any of you are an Emacs org-mode users, can you please tell me a way to do this in org-beamer. I will be very thankful.

Any pointers or help is highly appreciated.

Here is a sample slide code:

\documentclass[bigger]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{fixltx2e}
\usepackage{graphicx}
\usepackage{longtable}
\usepackage{float}
\usepackage{wrapfig}
\usepackage{soul}
\usepackage{textcomp}
\usepackage{marvosym}
\usepackage{wasysym}
\usepackage{latexsym}
\usepackage{amssymb}
\usepackage{hyperref}

\begin{frame} \frametitle{Models}
\label{sec-2_3}

\usebackgroundtemplate{\includegraphics[width=\paperwidth]{../images/crayons.png}}

\begin{itemize}
\item choose training data set
\item choose test data set
\item choose model
\item fit on training data set
\end{itemize}

\end{frame}

-
Please show me the minimal file. –  xport Dec 29 '10 at 13:19
Thank you @xport for your prompt reply. Please let me know if you need any more details. –  suncoolsu Dec 29 '10 at 13:34
Please show me the preamble too. :-) –  xport Dec 29 '10 at 13:34
I know most of you can are aware, but tug.org/pipermail/texhax/2007-March/008035.html is the link from where I got the idea. –  suncoolsu Dec 29 '10 at 13:35
sorry again! I am new to this forum, and still learning the rules. –  suncoolsu Dec 29 '10 at 13:37

I used images Sir Isaac Newton (rename it as newton.jpg) and Kitten (rename it as kitten.jpg)

The code snippet below is self-explanatory and I compiled using pdflatex.exe because of .jpg format.

\documentclass[bigger]{beamer}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\usepackage{graphicx}

%Global Background must be put in preamble
\usebackgroundtemplate%
{%
\includegraphics[width=\paperwidth,height=\paperheight]{newton.jpg}%
}

\begin{document}

\begin{frame}{Introduction}
\begin{itemize}
\item 1
\item 2
\item 3
\end{itemize}
\end{frame}

% Local background must be enclosed by curly braces for grouping.
{
\usebackgroundtemplate{\includegraphics[width=\paperwidth]{kitten.jpg}}%
\begin{frame}{Kitten}
\begin{itemize}
\item 1
\item 2
\item 3
\end{itemize}
\end{frame}
}

\begin{frame}{Summary}
\begin{itemize}
\item 1
\item 2
\item 3
\end{itemize}
\end{frame}

\end{document}

-
. Since you responded the first, I am accepting your answer as correct. (I know Stefan came with the answer first, but my nuances delayed your reply. Thank you) –  suncoolsu Dec 29 '10 at 14:19
I takes time to produce more details answer. :-) –  xport Dec 29 '10 at 14:54
gosh \usebackgroundtemplate{}? that makes things so easy. man, i love beamer. –  asia1281 Mar 6 '12 at 23:00

Write \usebackgroundtemplate before the frame, not within:

\end{frame}
% Now we install the new template for the following frames:
\usebackgroundtemplate{%
\includegraphics[width=\paperwidth,height=\paperheight]{crayons}}
\begin{frame}
...
\end{frame}
% Now we install another template, effective from now on:
\usebackgroundtemplate{...}


Ensure that \includegraphics is able to find the image file, since you used ../images/crayons.png.

-
Works like a charm. Thank you @Stefan Kottwitz. Much appreciated. –  suncoolsu Dec 29 '10 at 13:52
I quick question. If I don't need a background, I use a file name which doesn't exist. I am sure there is a better way of doing this. Can you pls enlighten me again? –  suncoolsu Dec 29 '10 at 14:23
@suncoolsu: Just use an empty argument: \usebackgroundtemplate{}. –  Stefan Kottwitz Dec 29 '10 at 14:56