I saw some apps like twitter having recent tweets on Live Tiles. The Tiles are rectangle and occupy whole space and not square like all other apps. How to change or create the rectangle Live tiles..? Any idea?
It is currently not possible to have the rectangle tile. With version 7.8 and 8 apps will have the ability to have multiple size tiles. With 7.5 we are limited to just the square tile. With the square tile you can put into on the back tile. To update the tile see the Tile Overview sample on msdn. You can download the complete sample here.