Hi,
Welcome to Story Maps Hope you will like it.
I am not sure if iCloud support well to serve picture over HTTP, Dropbox is really good for that.
Your CSV item doesn't seems to be public. But that's ok, you don't have to create a CSV item to use a CSV to build your Tour, you can just start the builder from the Story Maps website and drag and drop the csv in the application. The application will help you troubleshoot your CSV. Note that you can also get an example CSV that will save you issue with naming of fields.
Also note that to use pictures hosted on any server, you don't have to use a CSV, you can build your tour from the builder by starting from scratch and the builder will prompt you to enter the point one by one.
Also note that if you have an ArcGIS Online Organization account you can store your picture in ArcGIS Online. That's the most secured way to keep your pictures really private.
Start creating your tour through that page Apps | Story Maps by clicking build your tour.
To use a CSV or build your tour point by point, on the first screen select the advanced option (at the right of YouTube).