Specifying a backgroundImage: Embed(source="/assets/bg.png"); will stretch the image, sclae it or do other weird things with it. I don't understand how this is a usable option for a scalable interface.
I am not the only person with this problem so I Googled and found some approaches (this one being quite tricky), of which one seemed to work, at least a little bit :-).
So I tweaked Jeremy's example a bit and came up with this. It uses Jeremy's approach of creating a BitmapData object and Shape and 'painting' into it with a linked image tile.
You can get my sources here and see the demo here (click the button to show the background graphic). I am open to suggestions and comments regarding this approach, it may be resource intensive (maybe not) although my tests showed only a 200KB increase in memory after the graphic was loaded.

You can see it here:
http://renaun.com/blog/flex-components/repeatingim...
http://labs.flexcoders.nl/?p=16
It would be nice to be able to set the image via MXML, maybe via the backgroundImage="" attribute rather than coding it into the class. Just an idea.
cheers
I took the code from Maikel and made it so all you have to do is set the borderSkin and backgroundImage styles of the Application component and it works. Check it out here:
http://renaun.com/blog/2006/12/08/165/
Maikel thanks for the code and idea.
I've updated the code. Now you can use it not only the Application, but also Canvas, VBox, HBox, etc...
http://labs.flexcoders.nl/?p=21
Thanks!
btw. ne of u guys tried using a 1 pixel line and stretching it as a background?
backgroundSize*
backgroundImage*
properties in the containers..
I was trying to do a background tiling but Flex did not behave as expected. A small problem like this took me a whole day, and then I run into you program solution. Thank you very much.
Hassan