I am not sure whether content is must nowadays since I have signed up for adsense 4 years ago.But I saw lots of image or video only sites using adsense.
You need content content content to use adsense on your website BECAUSE adsense is a contextual tool, it changes depend on your content.
a simple question , if you got only images on you website , how the hell google will know what adds it should show on your website? what niche of adds to display. what is your website related to?