tedster - 3:35 am on Jul 11, 2012 (gmt 0)
Certainly Image Search results in a lot of "one hit wonders" - and therefore a high bounce rate. But Image Search isn't the regular organic search and Google certainly knows the average stats for image traffic.
I would have no concern about this - especially if you're looking at image traffic to be the cause of a Panda, Penguin or penalty problem. I'm certain that cannot be the case.