This file was created by "N9.大海" from here "http://bbs.dospy.com/forum-464-1.html"

Unzip it, go into "/usr/share/themes/base/meegotouch/libmeegotouchhome/style"

Backup your original "libmeegotouchviews-modified-default.css"

Overwrite with file within the zip file.

Then go to this directory "/usr/share/themes/blanco/meegotouch/images/backgrounds"

Place your designated background pic and name it after (must) "meegotouch-desktop-bg.png" (480x854)

Done, this changes all three swipe windows.

To undo it, just use the original css file
OR simply make "meegotouch-desktop-bg.png" a whole black background picture