In the last few days, Microsoft released the new Azure Active Directory Sign in look and feel experience to the public.
The new experience Is now the same for Azure AD accounts and Microsoft Accounts which was the goal of releasing the new experience, however, there Is one change that you will notice, the first screen only takes the user name details as shown below:
Once the user name has been confirmed you will forward to the next screen where you will be asked to enter your password.
For the next few months, the old sign in experience will available as well.
If you have a custom sign in logo it should work and there is no need to modify anything.