STEPS IN MAKING A “USB BACKGROUND IMAGE”
1- Look for a jpg image for your background…
2- Copy that jpg image onto your USB disk…
3- Open a notepad
4- Copy the codes below onto your notepad:

[ExtShellFolderViews]
{BE098140-A513-11D0-A3A4-00C04FD706EC}={ BE098140-A513-11D0-A3A4-00C04FD706EC}
[{BE098140-A513-11D0-A3A4-00C04FD706EC}]
Attributes=1
IconArea_Image=bird.jpg

6- Change the title of the image in codes above (IconArea_Image=bird.jpg) Replace “bird.jpg” to whatever title of the jpg image you saved earlier into your USB.
7- Save the notepad file as “desktop.ini”(don’t write, of course. the double quotation marks) into your USB.
8- Right click in the USB area and click “refresh”. It’s done!

credits: juntariman.wordpress.com