Hi

Below is an example of an override of RegisterRoutes in Global.asax.cs that does the replacement of media route

 protected override void RegisterRoutes(System.Web.Routing.RouteCollection routes)
        {
            base.RegisterRoutes(routes);
            int mediaRouteIndex = 0;
            //Find out index of media route so we can replace it at same location
            for (int i =0 ; i <routes.Count; i++)
            {
                var contentRoute = routes[i] as ContentRoute;
                if (contentRoute != null && contentRoute.Name.Equals("Media_Global"))
                {
                    mediaRouteIndex = i;
                    break;
                }
            }

            if (mediaRouteIndex != 0)
            {
                routes.RemoveAt(mediaRouteIndex);
                routes.MapContentRoute(
                    name: "Media_Global",
                    url:  "media/{node}/{partial}/{action}",
                    defaults: new { action = "index" },
                    contentRootResolver: sd => sd.GlobalAssetsRoot);
                //The media route is now added last, move it to previous location
                var mediaRoute = routes.Last();
                routes.RemoveAt(routes.Count - 1);
                routes.Insert(mediaRouteIndex, mediaRoute);
            }
        }

Thanks Johan, works like a charm!