Sometime it can be very useful to change the background of a Windows folder, for example to see white icons like the one generally used for ApplicationBar buttons in WP8 development.
If the default theme is set, the folder looks like as following, where you can badly see the picture of each icon only when the mouse is on it.

Folder containing icons for WP8

Unfortunately it is not possible anymore to write a specific desktop.ini file inside a folder to change its features like its background, as it was possible in Windows XP and Windows 7.

The only way I found is to temporary change the theme for all the windows, choosing a Hight Contrast one, as explained here. Perhaps in a future Windows 8 release a specific way to personalize a single folder will be introduced.
In the meanwhile the result is the following for all folders … so you better have to reset the theme after you choose the appropriate icons!

Folder containing icons for WP8 (Hight Contrast theme)

If your purpose is only to see white icons, you can simply select all the files (cntl + a) in the File Explorer and , more or less, you can distinguish the figures …

simply selecting all the files in the File Explorer (cntl + a)