In bb2 your able to animate objects... There's a tut on their YouTube channel in the special event walk through I think...
Create a scene and mute is with M. This way that scene will not be displayed on your game. You can also adjust the Start and End Distance of it to 0 so it will be no way BB will ever display that scene during the gameplay, even if you forget to mute it. Name that Scene as "Main Menu Background" Now go to Menu editor, and select Main Menu (single click only, do not open the Main Menu editor just yet). On Background Scene select Main Menu Background. Go back to the Scene Editor. Now you can add an object to the Main Menu Background scene that rotates... Place it in a way that it goes directly under your button...
A png sequence is like any animation sequence. Except that this one takes up the entire screen instead of being a character. Here is an example, note how the pages are numbered in sequence. Changes of image on each screen is subtlety different.