The first thing that many developers (and more designers) worry about when first researching Flex 2 is the default appearance of Flex applications. So many Flex 2 demos use the default theme that it may look like you have no options: your application can look like whatever you want, as long as it's blue-green with rounded edges and Verdana. If this were the case, then you'd have a hard time convincing any client to let you use Flex 2!
Thankfully, that's not the case. Without too much effort, you can make Flex 2 applications that look nothing like the defaults. In the real world, making your application look good can be just as important as making it functional.
There's only so much you can do with the built-in style properties. You can change borders, colors and spacing, but to really change the appearance of your application, you'll need assets.
Flex 2 handles assets very differently from, say, Flash 8. For one thing, Flex 2 compiles straight from source files. The IDE doesn't have any library panel or interface for importing assets. Though it may not appear so at first glance, Flex 2 is quite capable of including multimedia content with your code in compiled SWFs.
You can embed fonts, sounds, graphics, and even other SWFs in your application. When embedding assets into an application, you don't get an opportunity to control quality settings, so if you have control over the compression settings of these files, you must tweak these using external programs. ...