Like TiledBGs, sizing margins will reduce the number of objects u need for create your game
like this:
Red = Edges, Fixed Image
Blue = Borders, Tile/Stretch
Black = Middle, Tile/Stretch
etc..
u setup images/margins like this:
123
456
789
when your resize, it automacally does this
12223
45556
45556
78889
and the possibility of selecting from Tile to Strech mode
i searched and didnt find nothing related to it, so i suggested it