João Luís

WordPress allows you to define a site logo (through Jetpack) and a site icon, why would you need to upload another image to use in your login page?
This plugin allows you to forget the login page. Just activate it and all the magic is done for you. No extra steps required.
The plugins uses the site logo if it exists, otherwise it will use the site icon. If none of them exist, the plugin will not touch your login page.

JL Login Logo

Uses your site logo (defined through Jetpack) or your site icon as the logo on the login form.

Dominik Schilling

required

This plugin helps you to declutter your WordPress admin by removing all Jetpack related notices that promote services like the backup services VaultPress, WordPress Apps or Blaze.

Jetpack Without Promotions

WordPress dashboard is a stage for abusive use of screen estate. The fact that Jetpack, a plugin by the company that confuses itself with WordPress, is leading the way in this abusive use is just wrong, a shame really, and setting the wrong example for all plugin and theme authors.

WordPress urgently needs a way to put this nags where they belong: the plugin/theme specific settings page or some kind of notification center.

Thank you Required for helping to clean up. It is not a definitive solution but it is a welcome panacea.

The plugin that should not be

Removes all admin notices for promotions added by Jetpack.

JL Login Logo vs Jetpack Without Promotions