I've always just used the article document class when creating posters.
Here is a style file I have used:
---------------begin scifiposter.sty----------------------------
\renewcommand\Huge{\@setfontsize\Huge{30}{36}}
\newcommand\Giant{\@setfontsize\Giant{50}{54}}
\textwidth=7in
\textheight=9in
\oddsidemargin=-.25in
\evensidemargin=-.25in
\topmargin=-.5in
%\marginparwidth=1.25in
%\parskip
\pagestyle{empty}
\nofiles
---------------end scifiposter.sty----------------------------
And here is a typical poster I made:
---------------begin Carnival_Of_Souls.tex--------------------
\documentclass[12pt]{article}
\usepackage{times}
\usepackage{graphicx}
\usepackage{picinpar}
\usepackage{../scifiposter}
\begin{document}
\begin{centering}
{\Huge \textbf{The Wendell Free Library Presents \\ the next in the series \\
of Science Fiction / Horror movies:\\
\textit{Carnival of Souls}\\
Saturday, December 15th, 2012 7:30PM\\}}
\vspace*{.25in}
\end{centering}
\begin{window}[0,l,\includegraphics[height=4.5in]{Carnival_Of_Souls.jpg},]
{\Large Mary Henry is enjoying the day by riding around in a car with two
friends. When challenged to a drag, the women accept, but are forced
off of a bridge. It appears that all are drowned, until Mary, quite
some time later, amazingly emerges from the river. After recovering,
Mary accepts a job in a new town as a church organist, only to be
dogged by a mysterious phantom figure that seems to reside in an old
run-down pavilion. It is here that Mary must confront the personal
demons of her spiritual insouciance.
\vspace*{12pt}
There will be a short (1/2 hour) film before the movie: ``Rocky Jones,
space ranger, part 1. Beyond the curtain of space'', from the 50's
Rocky Jones TV series.}\\
\vspace*{.5in}
\end{window}
\vfill
This is the next in the monthly series of Science Fiction/Fantasy and
Horror/Monster movies at the Wendell Free Library, located in the
center of Wendell, MA. Free Admission. For more information about the
Wendell Free Library visit its web page at
www.wendellfreelibrary.org
or call
978-544-3559.
\end{document}
---------------end Carnival_Of_Souls.tex----------------------
>
> Thanks
>
>
> --
> Alexis Praga
>
>
--
Robert Heller --
978-544-6933 /
hel...@deepsoft.com
Deepwoods Software --
http://www.deepsoft.com/
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