With the new Openbox coming and the new PCManFM package, new tricks are to be setup.
In order to get background, transparency in panel, and icons all at same time:
Now the novelty is to have a .xsession file in your home with permissions set to 755 and theses lines in it:
# Executed by startx (run your windows manager from here)
/usr/bin/pcmanfm --desktop -d &
feh --bg-scale ~/.local/wallpapers/your_image_name.png &
exec ck-launch-session openbox-session
In the above script, you can see pcmanfm started to manage desktop and icons, and feh started to manage background. You will set pcmanfm to use the same background : from the right-click openbox menu "Preferences > Desktop-prefs"
You will then go to GDM login and set up GDM to use Xscripts.
Alternately you can use feh alone : then no icons. Or you can use idesk to manage icons. Not that easy but after reading the README in the config directory we can work it out.
You could also set the background to be shown by nitrogen : well, feh is fun too, look at the comments in the .config/openbox/autostart.sh file.
One more thing for people liking icons : now they can be moved around on the destkop !
For thoses who like to have a few effects in their desktop : I installed the dana version of xcompmgr, along with Calimeroteknik's bash script : which allows having more effects and having them available in the right-click Openbox menu in the Preferences menus. Of course, no comparision with what Compiz can do. It's much lighter, of course.