I have noticed alot of fluctuations in SERPs these two months and see you guys too but If you drop in Web SERPs your image search positions still stay.
Looks like something was updated yesterday as i got a new image as top 3, it wasnt there before! And for the last 3 months i got more 3 images in top 5! No drops for image search, all stable, only gaining. The image traffic is bad though as far as conversions, mostely people steal the photo