Here is some additional info from Google Schwartz says for Bing, you should name the images properly and upload product categories for eCommerce images.

Enge suggested some even more basic tried and true SEO tactics that should still be applied. Include alt attributes in img source tags. Name files appropriately, and consider the nearby text, overall page context, links, title tags, etc. This stuff is all good, but you should know that the way search engines are handling images is evolving.