Perfect Background

This is driving me crazy. Im doin a FBF and I wanna have a 100% picture in the background. Th problem is, when I scale the flash I want the picture to scale “untouched” with it.

Good examples:
http://www.diesel.com/
http://www.gskinner.com/site2_5/

Ok example
http://www.setvariable.com/elastic/

NO GOOD EXAMPLES:
http://www.secondstory.com/
http://www.revolvercreative.com/flash.html

can somebody PLEASE help me - Im goin crazy!!!