Change Your Wp-Admin, wp-login Logo, Custom Link And BACKGROUND
Using this small plugin you'll be able to change:
You need to insert your custom logo URL and Enable the Function
In the "0.5" Version you will also able to change the Default "Wp-admin" Link (to wordpress.org) with your Own Home Page Link, simply setting the custom url from the dropdown menu.
Edit Your Wp-login background
You do not need to do any other change.