I am working on a tabbed series map and wish to use custom icons. I downloaded them from www.mapicons, added them to my content, shared them and pasted the url into where it says in add image. After clicking OK, then Close. My icon does not change.

My map is at http://arcg.is/1fpdbWA The icon is on the Welcome Tab and goes to a pop-up entitled agricultural lands. The current icon is a tree with a sign.