New
#1
Get rid of login background completely
If you just want a totally blank (say black background) also without the "grumpy cyclops" or a personal picture, then easy to do now without any registry changes etc.
Create a .png file using pbrush and create a black (or any colour you like) picture (large rectangle filled in with you olour choice)
Select that as the lockscreen background (even if you do not actually show the lockscreen)
Make sure setting is set to show lockscreen on login screen
Select same .png file as above as your picture in accounts, info
Now when you boot you get a totally blank background.