The Problem
You want to customize the images displayed for the CQ5.5 login pageThe Solution
You need to take a copy of the libs/cq/core/content/login node, and copy it to apps/cq/core/content/login.
If you don't already have the following folder structure, create the following by going to localhost:4502/crxde
Right click on apps, create folder and call it:
cq
right click on the newly created cq folder, and create a new folder named:
core
right click on core, and create a content folder
go to /libs/cq/core/content/login, copy the folder, and paste it into your newly created core folder.
You should see the following:
To replace the background of the login page, replace background.png with an image of your choice.
Do the same for all of the relevant background screens.
The images folder contains all of the additional images for the login screen. You can go through these one by one to customize the page.
If your desired customization needs to go further than simply replacing images, you can change the login.css and login_ie.css style sheets.