There are a couple of bungee hooks on your pillion pegs.
Not sure if there are more hook-points on the standard snow-shovel monstrosity too - got rid of mine for an undertray.
If you're thinking of panniers though, I have the oxford ones and with all the straps they are already pretty sturdy when fitted - i just fitted two more bungees between the front-end of the bags and the pillion pegs, and then for the rear-end I sort of bungee'd them to each other with the straps wrapped underneath the tail of the bike, behind the number plate. Hope that makes sense!
If you've still got your grab-rail I'm sure an extra bungee wrapped around that somehow wouldn't hurt.
Oh by the way, put something between the bags and your paintwork! Some of that non-slip webbing stuff is perfect, stops the paint getting scratched.
EDIT - beaten to it while typing!
