Here's a cheapie: Animated smoke buttons.
Create a seamless loop by removing a chunk of the left of the art, dropping in in a layer and moving it to the right, then fading out the left part of the chunk so that it blends in. Then flatten it, crop out the space that the chunk came from and you have your loop. When creating the animation, use the Actions section of the Inspector to set the group to ignore pointer actions. You can then duplicate the button and offset the animation to provide variety among the buttons.
AnimatedSmokeButtons.hype.zip (24.4 KB)