Nah, im not seeing to much change. But I dont get most of my visitors from images so I guess it doesnt matter for me~
I'm seeing the opposite - haven't had traffic from google images for ages, but I've been picking some up this week. Google seems to give the images search a major update every 3- 4 months - I've never seen any sources on this, that's my perception from my own traffic and what I've noticed from when I've redesigned sites. Although- it's hard to do anything useful with that traffic - people looking for an image just want to see the picture, they don't often have any interest in the site it comes from.
I've noticed scarry changes there twice in the past two weeks. I had images on 1st page (#1, #2, and other positions) from two totally non-related sites, and they all dissappeared (and were even de-indexed!) for a couple of days or so. But then they all came back without position change. Checking now...everything just fine .