Artist Doug McFarland shares this info:
An analysis of my traffic shows that a good 10% to 15% of my sessions are coming from images.google.com, for me that is an additional 200 visitors a week that arrive based on an artwork tag and a location. In fact, the image referral sessions are about the same as keyword referrals (now).
Sounds like a darned good reason to title your works and use ALT tags for your images.
Image: (c)Doug McFarland