http://www.arpitonline.com/blog/2009/03/21/flex-builder-tip-use-swcs-for-image-assets-not-embed-metatags-for-pure-actionscript-projects/

PS

What is Flex Assets?

When using [Embed] to store some bitmap, it will extends BitmapAssets, etc……….

so somethime may not want to use Embed tag, then u can import the Asset class inside and extends by yrself!

http://www.ultrashock.com/forums/flex/embed-flex-assets-without-using-flex-123405.html