"This is not a VPK and you need to do this manually"

Also you don't need to use GCFScape to open it. Just extract the bik file.

Then Go to:
[C:\Program Files (x86)\Steam\SteamApps\common\left 4 dead 2\left4dead2\media]

1. Make sure you backup the these files "l4d2_background01, l4d2_background02, l4d2_background03, l4d2_background04, l4d2_background05"
2. Rename the file you've just downloaded to this "l4d2_background01"
3. Then create another one of that file until you have 5 copies.
	This is the Example:
			l4d2_background01
			l4d2_background02
			l4d2_background03
			l4d2_background04
			l4d2_background05

ENJOY!!