Hello Kieran,
I think that Apple's silent rule on this is that we won't be able to set a background color or image under "All My Files". With the addition of "All My Files" in Finder, Apple is obviously trying to provide an alternative way for users to have a quick and comprehensive overview of all the files on your Mac. That part of it may be obvious to most, but what isn’t readily apparent –and what has been downright confusing to some of us- is how these added options affect the other folders on your Mac. So, just a quick explanation of what this means as I understand it (and my apologies if I seem to be making some obvious points for the sake of explaining):
With the number of files that would be found under "All My Files" for most users, it makes sense that Apple has opted to change up the view a bit in “All My Files”. They’ve done this by breaking up the page into categories (e.g."Name," "Kind," "Application," et cetera) that are set apart by horizontal lines (effectively, Cover Flow-like navigatable icons set in rows). Many of us might not see the purpose in this, but it does make sense for navigating larger folders. Think of it as a combined look of the list view and Cover Flow. When considering those other views (list and column view, for example), you will realize that you cannot apply background images or colors to those views. Therefore, it seems that Apple has decided to treat this view option similar to the List or Columns view, excluding any additional visual or graphical content (i.e. colors or images) that would perhaps compete with an already busy look on the page. What seems to confuse many of us who wonder what has happened to our background images and colors when browsing in the icon view in Finder is that we don’t realize that we’ve selected (or Lion has selected for us) any “Arrange By” criteria, or we expect the “Arrange By” options in icon view to not affect the background image or color because we are in icon view where our background image or color for any particular folder is usually seen.
I hope that adds some clarity to this issue,even if we can’t accept the fact that we seem to lose some of our more customizable and personalized options in Finder while gaining some more functionality in how we are able browse our files.
Ryne