When to use IMG vs. CSS background-image?

Answer 1

One more benefit from using the tag is related to SEO - i.e. you can provide additional information about the image in the ALT attribute of the image tag, while there's no way to provide such information when specifying the image through CSS and in that case only the image file name may be indexed by search engines. The ALT attribute definitely gives the tag SEO advantage over the CSS approach. That's why according to me it is better to specify the images you want to rank well in the image search results (e.g. Google Image Search) using the tag.