Ubuntu Tweak: Ubuntu Tweak is a third party software that easily allows you to change themes and settings for windows, the startup screen, etc. This is GUI friendly for those of us who are still unfamiliar or not use to working through the Command Line Window or Terminal. Ubuntu Tweak can be found here for downlaod: Ubuntu Tweak. Although, it is supposed to be available under the Ubuntu Software Center repositories, I couldn't find it. Supposedly, you should go under to Edit --> Software Sources, then to the Other Sources Tab and click the two options, that aren't checked (http://archive.canonical.com/ubuntu; http://archive.canonical.com/ubuntu). However, this did not work for me so I simply googled and typed in Ubuntu Tweak and went to the website for the download. It works great. I used it to change the Login Window screen background since I could not do it through System --> Administration --> Login Screen (which use to be Login Window and there use to be a tab under the Software Sources named Third Party Sources so don't freak out if they are or are not there, like me :) ). Also, I couldn't find where Ubuntu Tweak installs for a few seconds. It is under Applications --> System Tools.
A few websites to hopefully help out if needed:
Change the login screen background in Ubuntu 10.04 nfolamp blog (this is where I found Ubuntu Tweak)
Ubuntu Forums (.org): A forum I repeatably come across when googling stuff about Ubuntu
I was trying to find the Configuration Editor under System Tools in order to follow some instructions for changing the splash screen (from what I understand the splash screen is the screen during loading). It wasn't there so I googled it and came across a post on Ubuntu Forums about the splash screen. Someone posted a few posts down how they couldn't find their System Tools menu and lots couldn't find in the GUI the Configuration Editor but could find it in the terminal. Someone graciously replied to go to System --> Preferences --> Menu Layout. However, in the latest Ubuntu 10.04 LTS, it is under System --> Preferences --> Main Menu, :).