The dialogue box for adding pictures to a Story Map TOUR does not appear to have "URL" option like the Series and Journal Story Maps. As such, my students and I were confused how we can use our Office365 Online accounts (where they store images etc). We tried the cog-wheel icon but that got confusing very quickly. Thankfully, we continued on to the Series Map demo and found that it has a "URL" option.
I would strongly recommend someone add the "URL" option to Story Map Tour to match the others. We aren't really allowed to encourage our students to use Flickr as we haven't vetted their Terms & Conditions etc.