We use web maps to present our image services to the public, because they have most of the functionality we need and the out-of-the-box apps don't support some of these needs (like access to raster processing templates).
I would like to have the ability to add a splash screen to our web maps directly, rather than having to rely on users accessing the maps through a StoryMap or web application. Recently, I wanted to inform users that service performance would be degraded during a planned update, and wasn't really sure how to go about it. It would be great to have the option to display a splash screen with that kind of information.
In the new Map Viewer, I was able to add a media file as a layer (took a screen shot of the message I wanted to display and uploaded the PNG), and essentially treat that as a pseudo splash-screen. At the end of the message, I directed users to turn off the layer in the Layers list to close the message. While this will likely do the trick for now, it's not ideal.
I haven't yet found a similar workaround to use in Map Viewer Classic (which we still have to use because the popups for image services don't always display at all locations on the map in the new Map Viewer - Esri bug report is here). I don't imagine that there will likely be any new features added to Classic, but if anyone has a good splash screen work around, please let me know!
