Stylish Login Pro is a simple modern plugin I made so that I could customize the login screen on my own website by utilizing in-built WordPress functions and the WordPress media uploader.
Stylish Login Pro allows you to customize your admin by adding your own logo to the header. It also replaces the WordPress logo on the login screen with the same custom logo. Also it gives a modern Flat UI to the Login page.
If you are a web developer you can even edit the CSS manually if you like.