Tired of using default user account thumbnails on your windows xp? Here’s the solution.
1. Choose your favorite picture, it should be fairly square, the resolution of each thumbnail should be 48 by 48 pixels. To edit or modify its resolution, you can use any picture tools such as Microsoft office picture manager, Adobe Photoshop etc. To have a better clarity of your image, make sure that it was set to bitmap file or it should have .bmp extension.
2. Once you already have your picture, you can put it on this folder.
C:\Documents and Settings\All Users\Application Data\Microsoft\User Account Pictures\Default Pictures (Application Data is a hidden folder)
That is the place where your default thumbnails were located, you can try putting your pic into that folder.
3. Hit the Start Button then click the user accounts picture and it will bring you to a new window that tells you to choose another pic for your account, look for the one you just created select it, and click the "change picture" button and you're all set!.