I have been working with map image layers and I love the ability to make pop up changes in one map and have the changes fillter out into other maps that contain the same map image layer. I was doing some more testing and I noticed that I can do this with visibility range but not with transparency. It seems like transparency should also be able to change in one map image layer and filter across to other web maps becasue when I change transparency the "Save Layer" button at the bottom of the options drop down becomes un-reyed out. Bellow I have put a description of how I use map image layers to make changes to pop ups across multiple maps to help clearify my idea.
Now the very handy part of using map image layers. Lets say we add a map image layer called "HSIP Boundaries Federal" to two maps, "map A" and "map B".
Now the pop ups for all of the layers in this HSIP Service are disabled. So I enable pop ups on all of the layers in map A. Here is the magical part, if I click the "Save Layer" button at the bottom of the options list the changes I just made will show up in map B!
This functionality works with Pop up configurations, and visibility range. Unfortunately it does not work with transparency.
Hope you find this helpful,