for the icons and folder icons KEEP the Bundles folder, as for the dock im assuming youre talking the black bar going across (above the docked icon). Thats the Wallpaper.png and you need to keep that UNLESS you want a different background/wallpaper. you can delete the UIImages folder, Extras (if one) and if you dont want the "startup" screen the delete the Folders folder
If i want a different background I can just delete the png files and use my own in my photo library from my phone can't i?