What do you mean 16.04 is no longer under development does that mean it can't be customized?
I know 16.04 has been finalized and released....
I 'll try those setting but I don't think there's a lot you can do to customize the login unless I'm wrong, I was in those setting a while back but I have to take another look
There is now a final release of 16.04, the next developmental version will be 16.10 and placed there. The current 16.04 developmental discussions will die out and be put to rest.
Your desktop will always be open to customization.