Thank you very much! Yeah, I typically use css background when building out banners, but when it comes to making websites semantically <img> tags are the way to go. Really you could use either one for banners, it's really personal preference.
A colleague started that infiniti banner, and did some of the setup. It was handed off to me to finish it up. He had already setup that sprite sheet with the copy, but I typically and prefer to work with svg. For that client I think we had to support older versions of IE which doesn't play nice with svg.