Ask has updated its image search with, it claims, more relevance, greater depth of coverage, and a new Patent Pending technique for image analysis, along with quality and content analysis to aid ranking.
There's an Ask-named "zoom" feature which allows closer investigation of the associated subjects. I tried this and it was interesting. I spend far too much time on that. ;)
It seems they are using image recognition technology to help rank images, along with the usual authority identification process.
It seemed to work for me, and the image quality was good, along with the "zoom" feature, it'll keep you busy for hours.