I should start off by saying I am fairly new to Linux. I want my pi to scroll through pictures in Image Viewer and never sleep. I've followed these instructions from another question to try to fix the sleeping problem.
apt-get install x11-xserver-utils
Now open up your ~/.xinitrc file
(if you don't have one then create it) and enter this:
xset s off # don't activate screensaver
xset -dpms # disable DPMS (Energy Star) features.
xset s noblank # don't blank the video device
exec /etc/alternatives/x-session-manager # start lxde
I didn't have the .xinitrc file in my home directory so I created one. It hasn't seemed to make a difference. I also have a .Xauthority file in /home/pi and have tried renaming it but it creates a new .Xauthority file.