A stencil for an animated background is a nice element for motion graphics. Unfortunately, the compositor is not always well-suited here. But Cycles comes for the rescue!
When I created this background stencil some time ago I found the lack of direct interaction with images in the Blender compositor both slowed me down and was outright annoying. But I found a nice workaround by using Cycles. Watch this tutorial if you want to find out how Cycles can help you in motion graphics work, even in realtime.
The finished .blend and the fire animation can be downloaded here!