# create 2GB image file (adjust size if desired)
dd if=/dev/zero of=/path/to/image_file bs=1M count=2048

# format image file with ext2 (or ext3 etc.)
mkfs.ext2 /path/to/image_file

# mount image
mount -o loop /path/to/image_file /mountpoint

# install base system (if you ommit --arch debootstrap will use the host's architecture, armel on an N900, armhf on a Cubieboard2; chose the Debian mirror closest to your location [1])
debootstrap --arch=armhf wheezy /mountpoint http://ftp.de.debian.org/debian

# copy /etc/apt sources.list and /etc/apt/apt.conf (I don't want suggests and recommends [2]) from host system
cp /etc/apt/sources.list /mountpoint/etc/apt/
cp /etc/apt/apt.conf /mountpoint/etc/apt/

# In the image /var/run is a symlink to /run. For pulseaudio and dbus to work we need this to be swapped (the missing /mountpoint in the last line is not a typo)
rm -rf /mountpoint/var/run
mkdir /mountpoint/var/run
rm -rf /mountpoint/run
ln -s /var/run /mountpoint/run

# we also need directories for pulse and dbus in /var/run
mkdir /mountpoint/var/pulse
mkdir /mountpoint/var/dbus

# replace standard keyboard layout in the chroot with N900 keyboard (assuming you are already on the N900)
rm -rf /mountpoint/usr/share/X11/xkb/*
cp -r /usr/share/X11/xkb/* /mountpoint/usr/share/X11/xkb/

# chroot into image (everything after this step will happen in the chroot unless indicated otherwise)
mount -o bind /proc /mountpoint/proc
mount -o bind /sys /mountpoint/sys
mount -o bind /dev/pts /mountpoint/dev/pts
chroot /mountpoint

# update apt and install additional required packages (add any packages you like)
apt-get update
apt-get install locales lxde-core dbus-x11 roxterm-gtk2 lxde-icon-theme xserver-xephyr bash-completion sudo libgtkstylus pulseaudio

# fix this locales warning we just received (adjust the locale if you wish; info from here [3])
export LANGUAGE=en_US.UTF-8
export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8
locale-gen en_US.UTF-8
dpkg-reconfigure locales

# replace Debian's pulseaudio packages with recompiled ones, either from the provided archive or your own ones (see [4])
dpkg -i pulseaudio_2.0-6.1_armhf.deb libpulse0_2.0-6.1_armhf.deb

# make sure they won't be overwritten by future Debian updates (note: if you use synaptic you have to hold them there as well because synaptic doesn't care for what dpkg says)
echo pulseaudio hold |dpkg --set-selections
echo libpulse0:armhf hold |dpkg --set-selections

# also hold xkb-data (this is where the keyboard layout comes from)
echo xkb-data hold |dpkg --set-selections

# you'll need these binaries for keyboard focus in the chroot (take them from the provided archive, an existing image you have, or compile them on your own; sources are here [5][6])
/sbin/qobi-wmhint-fix
/usr/bin/set-focus

# if you use the provided armel binaries on a armhf image you'll need this symlink (see [7])
ln -s /lib/ld-linux-armhf.so.3 /lib/ld-linux.so.3

# additionally you'll need a script that starts lxde on $DISPLAY :1 (again, take it from the archive or an old image)
/usr/bin/startlxde1
# for an unknown reason I had to add export GTK_MODULES=libgtkstylus.so here although it's supposed to be set in debbie-sue on the host; both versions are in the archive; I believe the rest of the scripts aren't necessary anymore, but I included them nevertheless in the archive