How to change the login screen background in Snow Leopard?
Since the time you have bought your Mac, you might have been seeing the same boring background of login screen. There is a small trick that can help you to change it. Here are the steps: 
1. Go to Finder and open ‘Go to Folder’ or you can also hit Command+Shift+G to open the same screen.
2. Now in the path, type /System/Library/CoreServices/ and click ‘Go’.
3. Once done, find the image file in the name of ‘DefaultDesktop.jpg’ and replace it with the image or file of your choice.
I would suggest to make a backup of the original file.
Also see the resolution of the image so that you can replace it accordingly and the new image looks perfectly fit to the screen.
That was all! Now you can reboot and try this hack, its wonderful. This trick works to change the login background in Mac OS X Snow Leopard 10.6 only. I know you are smart enough to find the file in Leopard also.
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Screen Size 10.1 Inch
Resolution Pixels 1024x600
Backlight Type LED
Aspect Ratio 16:9
Screen Surface Glossy
Data Connection 40-Pin
Application Laptop or Notebook
http://www.nbkit.com/Wholesale/product/New-AUO-B101AW02-V.3-LCD-screen-10.1-inch-LED-1024x600-WSVGA-with-Digitiser_c18950.html
AUO B101AW02 V.3 LCD screen LCD screen is the most important component of laptop.Maybe Other laptop parts or components could be replaced or repaired easily at low cost.but for LCD screen,in most cases it only can't be compatible problem. For solve the following problem,broken lcd screen,bad pixels,white lines,color,shine screen.Replace A LCD screen is only solution.Sometime,you need to make sure anti-static steps prepared before remove old screens and check new lcd screen parameters match your original LCD screen. so sugguest buyers need buy it at professional laptop screen website.
The LCD screen review from NBkit.com
10.1" wide screen has 3 kinds different resolution 1024 x576 1024x600 and 1366x768. the previous 2 kinds we called standard screen, and the later one we called HD version. Something we need to note is that once you put a screen 1024x600 on a 1024x576 laptop, you may see one black line on screen at bottom, it seems strange and looks not funny. 40 pin connector and LED backlight are the same feature of this 3 kinds screens. So they have good compatibilty each other, when you select correct resolution. 10.1 HD version is for some user like movie with netbooks. personally, 10.1 HD is not good , if you need HD , why not purchase 15.6 or 14.1 HD version? In addition, we have to refer to 10.2 wide screen here , because by NBkit.com statistics , many laptops do a mix 10.1" 10.2 " lcd screen in same laptops. for example HP Mini 1000 , you may find the screen may be N101N6-L01(40Pin) or CLAA102NA2CCN (30pin) or other screens. Some repair man will tell you the differenence if you want to do repair, but if you plan to do it self, that is you need to pay some attention. In a word, 10.1" , 10.2" are mainly part of netbook market.,up to 55% At last , 10.4" 10.6" wide screen is popular LCD screen for tablets in past 1-3 years. they usually has resolution at 1280*768 or 1280*800 . at very high price , good quality , LED or single CCFL lamps backlight, 14pin connector, 20 pin connector and 30pin connector. that you need to take care when you want do any repair or DIY replacing. Fujitsu tablet 10.6" or SONY 10.6 PCG-TR is the sample.