It was already working like that…my only issue was that when you change backgrounds, it was showing the old image, then the new image…now it shows no image…so it’s a feature that you had that is gone now…Here is a video I made yesterday to report the screen flashing but the solution should not be to just eliminate the custom screen! 
First you see old screen flash, then in the video where it says signing in is the new screen…but now that part of the sign-in visual is gone…please put it back as soon as possible. Sometimes app loads slowly so it gives the user something to look at - was a really great idea to have it!