The important issues to handle for such a project would be the handling of floats. Normally photo books or similar documents do not have a large amount of words and if you use floats and marginpars, the text will certainly end up in the wrong place.

I would first choose a few page designs and then use minipages or better TeX vbox and hbox primitives to position them and work macros around them. Martin's adjustbox package might also come handy here, i.e., you need to build the two columns, rather than use the marginpar area or a two-column layout.
The layout above was achieved using such a macro:
\newcommand\addpicture[2]{
\hskip-2cm\begin{minipage}[b]{17cm}
\includegraphics[width=17cm]{#1}
\end{minipage}\hspace{0.3cm}
\begin{minipage}[b]{3cm}
#2
\end{minipage}}
I haven't used your dimensions for the page geometry but you can vary the sizes in the minimal that follows. Add fonts and style to suit your requirements.
\documentclass[11pt]{book}
\usepackage{xcolor}
\usepackage{ifpdf}
\usepackage{graphicx}
\newfont{\HUGE}{cmr17 at 96pt}
\setlength{\textwidth}{8.0in}
\setlength{\textheight}{5.125in}
\setlength{\oddsidemargin}{0.0in}
\setlength{\evensidemargin}{-0.375in}
\setlength{\topmargin}{-0.375in}
\setlength{\headsep}{0.25in}
\setlength{\headheight}{0.125in}
\setlength{\footskip}{0.25in}
\ifpdf
\pdfpageheight 7.5in
\pdfpagewidth 9.625in
\fi
\newcommand{\hstroke}{\rule[0.5ex]{5.0em}{0.2ex}}
\begin{document}
\thispagestyle{empty}
\begin{center}
\setlength{\unitlength}{1.0em}%
\begin{picture}(45,16)(0,0)
\put(-0.625,0){\framebox(6.2,7.25){\HUGE \textcolor{purple}{A}}}
\put(5.875,5.625){\parbox[t]{15em}{\Huge \noindent LITTLE GIFT\linebreak
\raggedright FOR LITTLE\linebreak
FEET\linebreak
}}
\end{picture}
\hspace*{-0.6em}\rule{\textwidth}{0.3ex}\\
{\small \sc by}\\
{\small YIANNIS LAZARIDES}\\
{\footnotesize Author of ``Myths of TeX''}\\
\vspace*{18.5 ex}
\rule{\textwidth}{0.3ex}\\
{\small
DOHA\phantom{ZZZZZ,}\hfill\raisebox{0.5ex}{$\bullet$}\hfill THE CAMEL\linebreak
QATAR\hfill\raisebox{0.5ex}{$\bullet$}\hfill PRESS
}
\end{center}
\newpage
\thispagestyle{empty}
\vspace*{18ex}
\begin{center}
{\em Copyright, $\mit 2011$}\\
{\sc By the Little Girl \& Company}\\
\hstroke\\
{\em All rights reserved}\\
\vspace*{18ex}
{\sc A little story book}\\
{\sc for a little girl}\\
\vspace*{12ex}
Made in the wild.
\end{center}
\newpage
\frontmatter
\thispagestyle{empty}
\vspace*{20ex}
\begin{center}
{\scriptsize FOR}\\
{\large \bf Li, Mary and John}\\
\smallskip
{\footnotesize AND THE REST\\
OF THE WORLD'S\\
CHILDREN}
\end{center}
\mainmatter
\newcommand\addpicture[2]{
\hskip-2cm\begin{minipage}[b]{17cm}
\includegraphics[width=17cm]{#1}
\end{minipage}\hspace{0.3cm}
\begin{minipage}[b]{3cm}
#2
\end{minipage}}
\addpicture{children-03.jpg}{\ldots and on the other side of the world in the Land of the Moon Wi Li was sleeping \ldots}
\end{document}
See also Template for a book for children
octavo(I know is a bit heretical), but the class is very well documented and is based on the standardbookclass. Another problem will be floats, for a picture book I would not use them. Have you got a sample scan of what you are after? – yannisl Nov 01 '11 at 09:06!and a high-rep user will edit it back in. – doncherry Nov 01 '11 at 09:47![alt text][URL], but you can't save a post containing that while below 10 rep. But if you remove the!, you can save your post and a user with higher reputation can check the picture and edit the!back in, so that the picture will be displayed. – doncherry Nov 01 '11 at 10:43